問1題數學題~

(1)
Let the price of a lunch box be $x, and let the price of a glass of orange juice be $y.
2x+y=46---(1)
3x+2y=74---(2)
(1)x3-(2)x2:-y=-10
y=10---(3)
Sub (3) into (1):
2x+10=46
2x=36
x=18
Therefore x=18,y=10
Therefore the price of a lunch box is $18, the price of a glass of orange juice is $10.

2007-02-17 11:43:46 補充：
method of subsititution:Let the price of a lunch box be $x, and let the price of a glass of orange juice be $y.2x十y=46---(1)3x十2y=74---(2)From (1),y=46-2x---(3)Sub (3) into (2):3x十2(46-2x)=743x十92-4x=74-x=-18x=18---(4)Sub (4) into (3):y=46-2(18)=46-36=10

2007-02-17 11:43:55 補充：
Therefore x=18,y=10Therefore the price of a lunch box is $18, the price of a glass of orange juice is $10.

2007-02-17 11:46:26 補充：
以下又是另一種方法,但不知其名為何:Let the price of a lunch box be $x, and let the price of a glass of orange juice be $y.2x十y=46---(1)3x十2y=74---(2)From (1), y=46-2x---(3)From (2), y=(74-3x)/2---(4)Hence, 46-2x=(74-3x)/292-4x=74-3x-x=-18x=18---(5)Sub (5) into (3):y=46-2(18)=10

The prize of a lunch box is $18.
The prize of a glass of orange juice is $10.


I hope I can help you ! ^^

Let x be the price of lunch boxes
Let y be the price of orange juice

From John:
2x + y= 46
y = 46 - 2x

From May:
3x + 2y = 74

Then join them together

3x + 2( 46 - 2x ) = 74
3x + 92 - 4x = 74
-x = -18
x=18

After we know x = 18
Then we can also know that
2x + y = 46
36 + y = 46
y = 8

Therefore the price of lunch boxes is $18 and the price of a glass of orange juice is $8

2x+y=46 ----------------(1)
3x+2y=74 ---------------(2)
(1)x2
2(2x+y)=2(46)
4x+2y =92 ---------------(3)
(3)-(2)
4x+2y=92
-)3x+2y=74
__________
x = 18
Put x = 18 into (3)
4x+2y =92
4(18)+2y =92
72+2y = 92
2y = 20
y =10

the price of a lunch box is 18
the price of glasses of orange juicegor is 10

let x be the price of a lunch box and y be the price of a glass of orange juice

2x + y = 46 --- 1
3x + 2y = 74 --- 2

1) y = 46 - 2x

put 1 into 2

3x + 2(46 - 2x) = 74
3x + 92 - 4x = 74
-x + 92 = 74
18 = x
x = 18

put x = 18 into 1
y = 46 - 2(18)
= 46 - 36
= 10

so x = 18 and y = 10