一道概率题

Q24:
A certain restaurant offers 6 kinds of cheese and 2 kinds of fruit for its dessert platter. If
each dessert platter contains an equal number of kinds of cheese and kinds of fruit, how
many different dessert platters could the restaurant offer?
A. 8
B. 12
C. 15
D. 21
E. 27

看了许久，还是不明白为什么会得Ｅ呢．　我的算法：　Ｃ６．２＝１５

请ＮＮ指点吧．

1 cheese and 1 fruit    C6,1 * C2,1 = 6*2=12

2 cheese and 2 fruits    C6,2 * C2,2 =15*1 = 15

Total=12+15=27

Thanks, kingwangfei , for your timely reply , would you write in detaisl about your thinking for the question you answered .  I still have some puzzles to understand it better..

I have another question for anyone who can help me.

Q31:
If (2 -v5)x = -1, then x =
A. 2 + v5
B. 1 + (v5)/2
C. 1 – (v5)/2
D. 2 - v5
E. -2 - v5
Answer:Ａ

我得不出这个Ａ，请ＮＮ指点．