in a group of cows and hens , the number of legs are 18 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 ) + 18 4 x + 2 y = 2 x + 2 y + 18 2 x = 18 x = 9 . answer : c"
subtract(18, const_4)