in a group of cows and hens , the number of legs are 30 more than twice the number of heads . the number of cows is
"explanation : let the number of cows be x and the number of hens be y . then , 4 x + 2 y = 2 ( x + y ) + 30 4 x + 2 y = 2 x + 2 y + 30 2 x = 30 x = 15 answer : a"
subtract(30, const_4)