求解2题数学题: gwd21-20 和一道模拟题

gwd21-20: Of the 60 animals on a certain farm, 2/3 are either pigs or cows.How many of the animals are cows?

(1) The farm has more than twice as many cows as it has pigs.

(2) The farm has more than 12 pigs.

答案为C，为何A 不对？有题干可得40 只pigs or cows, 结合（1）可得这40 只能是cow, 若是40只pigs, cows 将是80只，而题干只有60 animals. 请nn 解惑。

模拟题：If xy=1, what is the value of [2(x+y)^2]/[2(x-y)^2] ?

a. 2     b.4     c.8     d.16     e.32

答案为d.该题无从下手，请nn 指教。先谢了。