[求助]PP的几道数学题，NN们帮忙看下吧~（新加了几道）

Amelia_21

1. 2/3 of 60 animals a firm has is either cow or pig, 求 how many cows?

the firm has more than twice as many cows as pigs

the firm has more than 12 pigs.

不知道思路对不对 设 cows: x ;pigs:y

则由（1）x>2y 由(2) y>12 x+y=40

联立 12<y<40/3 则y=13 进而可求x