急!!!~我又有幾條數吾識...幫幫我(20)

1. Let a be the amount she gave to Jason.

(66-a)/2=10.5+a

66-a = 21+2a

45 =3a

a=15

∴the amount Mary gives to Jason is $15

2. Let a be the amount of candies in the pile.

a/28 +1 =(a+8)/(28-5)

a/28 + 1 =(a+8)/23

23a/28+23 =a+8

23-8 =a-23a/28

15 =5a/28

a =15*28/5

a =84


∴the amount of candies in the pile is 84.

3. 1. Let a be the amount she gave to Jason.

(66-a)/2=10.5+a

66-a = 21+2a

45 =3a

a=15

∴the amount Mary gives to Jason is $15

2. Let a be the amount of candies in the pile.

a/28 +1 =(a+8)/(28-5)

a/28 + 1 =(a+8)/23

23a/28+23 =a+8

23-8 =a-23a/28

15 =5a/28

a =15*28/5

a =84


∴the amount of candies in the pile is 84.

3.(a) Let a be the amount of VIP tickets.

1500a+(15a+650)*800 =7,945,000

1500a+12,000a+520,000= 7,945,000

13500a =7,945,000-520,000

13500a/13500 =7425000/13500

a =550

∴ the amount of VIP tickets is 550.

3(b) Let a be the amount of standard tickets.

800a+550*1500 =7,945,000

800a+825,000 =7,945,000

800a =7,945,000-825,000

a =8900

∴ the number of standard tickets is 8900.

3(c) Let a be the number of free VIP tickets.

1200*800+1500a =1,140,000

960,000 +1500a =1,140,000

1500a =1,140,000/1500

a = 760

∴the number of free VIP tickets is 760.

2008-12-07 12:48:59 補充：
4. a/4-4=8

a/4 =12

a =48

5. ax+b=cx+d
ax-cx=d-b
x(a-c)=d-b
x=(d-b)/(a-c)
now x=2
x=(d-b)/(a-c)=2
d=8, b=2, a=7, c=4

2008-12-07 12:49:59 補充：
6. 2(2x+1)(x)=3x^2 +x(x-1)

2x *( 2x+1) =3x^2 +x^2 -x

4x^2+3x =4x^2

3x =0

x =0

2008-12-07 12:50:17 補充：
7. Let a be Tim's age, then 4a be Larry's age.

a+8+4a+8 =56

5a +16 =56

5a =56-16

5a =40

a =8

∴Tim's age is 8, and Larry's age is 8*4=32

2008-12-07 12:50:28 補充：
8. Let a be the length of the shorter wire, and (53-a)be the length of the longer one.

a/4 +6 =(53-a)/3

(a/4+6)*3 = 53-a

3a/4+18+a =53

7a/4 =53-18

a =35*(4/7)

a = 20

∴The length of the shorter wire is 20cm,and the longer one is 53-20 = 33cm.

2008-12-07 12:50:36 補充：
9. The value of X:

2X+(X+15)*3 =295

2X+3X =295-45

5X =250

X=50

10. Let a be the current age of Wesley.

( a-28)/4+18=28

( a-28)/4 =10

a-28 =40

a = 68

∴ the current age of Wesley is 68.

1. Mary has $ 66 and Jason $ 10.5. If Mary gives some of her money to jason, the amount Mary has will be 2 times that of Jason' s. How much does Mary give to Jason?

let x be the amount that mary give jason
66-x=2(10.5+x)
66-x=21+2x
3x=45
x=15

2.There is a pile of candies which can be evenly distributed to 28 children. If the number of candies increase by 8, and the number of children decreases by 5, then each child will gat 1 more candies. How many candiesare there in the pile?

let y be the number of candies in the pile
y/28+1=(y+8)/(28-5)
(28+y)/28=(y+8)/23
23(28+y)=28(y+8)
644+23y=28y+224
5y=420
y=84

3. The selling price of a standard ticket for a football match is $ 800, while that for a VIP ticket is $ 1500. The number of standard ticket is 650 more than 15 time of the number of VIP ticket. If all the ticket are sold, the total income will be $ 7945000?
3(a). Find the number of VIP ticket.

let a be the number of VIP ticket
1500a+(15a+650)*800=7945000
1500a+12000a+520000=7945000
13500a=7425000
a=550

3(b). Find the number of standard ticket.

as the number of VIP ticket is 550 (from a)
number of standard ticket =15*550+650=8900

3(c). Since the sales of ticket are not as good as expected, the organizer plans to give 1200 unsold standard ticket and some unsold VIP tickets to charities free of change. If the income of the match decreases by $1140000 because of this, find the number of free VIP ticketd.

let the number of free vip ticket be b
1200*800+1500b=1140000
1500b=180000
b=120

4.When you add a number to both sides of a lner equation in one unknow, then multiply both sides of the equation by the same number, the solution to the equation can be obtained. Set up an equation to satisfy the above?

x/2-2= 4
(add both side by 2
and then multiply both side by 2
then you can get x=12)

5.The root of the equation ax+b=cx+d is 2, where a, b, c and d are all non-zero integers. Find a set of values of a, b , c and d ?

ax+b=cx+d
ax-cx=d-b
x(a-c)=d-b
x=(d-b)/(a-c)
now x=2
x=(d-b)/(a-c)=2
d=8, b=2, a=7, c=4

1.
Let x be the amount Mary gives to Jason,
∴ 66-x = 2*(10.5 +x)
66-x = 21 +2x
45 = 3x
x = 15
∴the amount Mary gives to Jason is $15.

2.
Let n be the original no. of candies in the pile,
∵no. of candies get from 28 children each = (n≒28)
and no. of candies get from (28-5) children each when the number of candies increase by 8
= (n+8)≒(28-5)
∴(n≒28) +1 = (n+8)≒(28-5)
23n +644 = 28n +224
420 = 5n
n = 84
∴the original no. of candies in the pile is 84 units.

3.
a)
Let n be the no. of VIP tickets,
∴ (15n+650) be the no, of standard tickets,
∴ 800(15n +650) +1500n = 7945000
12000n +520000 +1500n = 7945000
13500n = 7425000
n = 550
∴no. of VIP tickets is 550 units.
b)
From (a), n = 550
∴no. of standars tickets = 15(550) +650 = 8900 units.
c)
Let p be the no. VIP tickets
∴ 1200(800) +1500n = 1140000
1500n = 180000
n = 120
∴the no. VIP tickets of free of change is 120 units.


我的信心有限，未能肯定最尾兩條的作答方法。

2008-12-08 00:34:26 補充：
4.
Let h be the value of unknow
h÷2 -2 = 4
h÷2 = 6
h = 12

2008-12-08 00:34:42 補充：
5.
ax+b = cx+d
ax-cx = d-b
x(a-c) = d-b
x=(d-b)÷(a-c)
now x=2
x=(d-b)/(a-c)=2
d=8, b=2, a=7, c=4

2008-12-08 00:35:41 補充：
6.
2(2x+1)(x)= 3x^2 +x(x-1)
4x^2+2x = 3x^2 +x^2 -x
3x = 0
x = 0

2008-12-08 00:35:55 補充：
7.
Let x be Tim's age, so that 4x be Larry's age.

x +8 +4x +8 = 56
5x +16 = 56
5x =56 -16
x =40÷5
x =8
∴Tim's age is 8, and Larry's age is (8＊4) = 32

2008-12-08 00:36:18 補充：
8.
Let d be the length of the shorter wire,
and (53-d) be the length of the longer one.
d÷4 +6 =(53 -d)÷3
(d÷4 +6)＊3 = 53 -d
3d÷4 +18 +d = 53
7d÷4 = 53 -18
d = 35＊4÷7
d = 20
∴The length of the shorter wire is 20cm, and the longer wire is (53-20) = 33cm.

2008-12-08 00:36:32 補充：
9.
The value of X is,
2X+(X+15)*3 = 295
2X+3X = 295 -45
X = 250 ÷5
X= 50

2008-12-08 00:37:01 補充：
10.
Let x be the current age of Wesley,
( x -28) ÷4 +18 = 28
x -28 = (28 -18)＊4
x = 40 +28
x = 68
∴ the current age of Wesley is 68.

2008-12-08 00:37:52 補充：
"＊/*"即是乘以

too hard
my mother and father also don't know
sorry