幫我解下呢2條數學題呀!(列式計算)!15點!!

1.薄餅一塊,弟弟先吃去1/4塊,姊姊再吃去1/6塊,兩人共吃去薄餅的幾分之幾?

A. 兩人共吃去薄餅的
= 1-(1/4)-(1/6)
= (12/12)-(3/12)-(2/12)
= (12-3-2)/12
= 5/12

2.花園裏種植了144朵花,玫瑰佔其中的1/4 ,當中有2/3是紅玫瑰, 紅玫瑰有多少朵?

A. 紅玫瑰有
= 144* 1/4 * 2/3
= 36 * 2/3
= 24朵

2010-03-12 18:41:16 補充：
Yahoo can't show the fraction so the question seems strange.

2010-03-13 17:25:38 補充：
Correction:
1.薄餅一塊,弟弟先吃去1/4塊,姊姊再吃去1/6塊,兩人共吃去薄餅的幾分之幾?

A. 兩人共吃去薄餅的
= 1-(1/4)-(1/6)
= (12/12)-(3/12)-(2/12)
= (12-3-2)/12
= 7/12
(5/4 = 1.25>1???
That means they have eaten more that 1 pizza?)

2010-03-13 17:30:02 補充：
Do I misunderstand the question?
薄餅一塊,弟弟先吃去1/4塊
= 餘下 3/4
姊姊再吃去1/6塊
= 3/4 - 1/6
= 9/12 - 2/12
= 7/12