急! 中一數學

1) Let x be the number of the smaller group
(60-x) be thr number of the larger group
7x = 3(60-x)
7x = 180-3x
10x = 180
x = 18
The number of stickers in the smaller group is 18.

2) Let x be the score of Wiliam's
(6500-x) br the score of Edward's
2x-1300 = 6500-x
3x = 7800
x = 2600
The score of Wiliam is 2600.

The score of Edward
= 6500-2600
= 3900

The difference
= 3900-2600
= 1300
so, Edward gets a higher score, by 1300 points.

3) Let x be the price of a pack of tissue paper
[since 1bk$=12tissue$
so, 3bk$=36tissue$]
3(12)x+6x = 105
36x+6x = 105
42x = 105
x = 2.5
The price of a pack of tissue paper is $2.5

The price of a book
= 2.5(12)
= $30

The price [of 4 bks and 2 packs of tissue]
= 4(30)+2(2.5)
= 120+5
= $125

1) Assume x = number of sticklers in the smaller group
and assume y = number of sticklers in the larger group

Equation A: x+y=60
y=60-x

Equation B: 7x=3y
substitute y=60-x into Equation B
7x=3(60-x)
7x=180-3x
10x=180
x=18 =number of sticklers in the smaller group


2) Assume x = Edward's point
and assume y = William's point

Equation A: x+y=6500
y=6500-x

Equation B: x+1300=2y
substitute y=6500-x into Equation B
x+1300=2(6500-x)
x+1300=13000-2x
3x=11700
x=3900 = Edward's point
y=6500-3900
y=2600 = William's point

You should be able to do the rest, right?


3) Assume x = price of a pack of tissue paper
and assume y = price of a book

Equation A: y=12x

Equation B: 3y+6x=105
substitute y=12x into Equation B
3(12x)+6x=105
42x=105
x=2.5 = price of a pack of tissue paper
y=12(2.5)
y=30 = price of a book

Calculate part (b) by yourself, OK?