中一數”急”(plz)

Donna buys some $2 stamps and $5 stamps.
If she spends $54 altogether and gets 15 stamps,
how many $2 stamps does she buy?
我要方程呀＞＜

[quote]原帖由 [i]bicky[/i] 於 2006-10-23 04:52 PM 發表
Donna buys some $2 stamps and $5 stamps.
If she spends $54 altogether and gets 15 stamps,
how many $2 stamps does she buy?
我要方程呀＞＜ [/quote]

[b][color=Red]設 佢 買 左 x 枚 $2 既 郵 票 ,
2x + 5(15-x) = 54
2x + 75 - 5x = 54
-3x = -21
3x = 21
x = 7
所 以 佢 買 左 7 枚 $2 既 郵 票 `

p.s.*
我 系 中 文 學 校 , s0 用 中 文 做 數 ,
h0pe 你 明 我 講 咩 :)[/color][/b]