In a group of cows and hens, the number of legs are 20 more than twice the number of heads. The number of cows is Select the correct option:
A) 5 B) 7 C) 10 D) 12 E) 14
Explanation:   Let the number of cows be x and the number of hens be y.   Then, 4x + 2y = 2 (x + y) + 20   4x + 2y = 2x + 2y + 20   2x = 20   x = 10   Answer: 10
<result>C</result>
In a group of cows and hens, the number of legs are 20 more than twice the number of heads. The number of cows is