一班小朋友合資買玩具,若每人付8元,便餘下3元;若每人付7元,則欠4元。玩具值多少元？

let x=小朋友
8x-3=7x+4
x=7
7*8-3=53元

Let x be the amount of the toy.
(x-3)/8=(x-4)/7
7(x-3)=8(x-4)
7x-21=8x-32
8x-7x=32-21
x=11
So the amount of the toy is $11

2006-12-21 21:35:08 補充：
Sor...Let x be the amount of the toy.(x-3)/8=(x+4)/77(x-3)=8(x+4)7x-21=8x+328x-7x=32+21x=53So the amount of the toy is $53.

let x=小朋友, y = 玩具值
(1) 8x-y=3
(2) 7x-y=-4
so (1) 8x-3 =y
into (2) 7x- (8x-3) = -4
y = -1x -3 = -4
1x =7
x=7

so (1) 8x-3 =y
7*8-3=53元

設玩具$x有n個小朋友
8n+3=x
7n+4=x

8n+3=7n+4
8n-7n=4-3
n=1

put n=1--〉7n+4=x
7(1)+4=x
x=11

or
put n=1--〉8n+3=x
8(1)+3=x
x=11
所以有1個小朋友買玩具，個玩具值11元…

2006-12-21 21:22:25 補充：
搞錯左，應該係：設玩具$x有n個小朋友8n-3=x7n 4=x8n-3=7n 48n-7n=4 3n=7put n=7--〉7n 4=x7(7) 4=xx=54orput n=7--〉8n 3=x8(7) 3=xx=54所以有7個小朋友買玩具，個玩具值54元…又或者：只設有n個小朋友8n-3=7n 4n=77×8-3=53都係有7個小朋友買玩具，個玩具值54元…