carl can wash all the windows of his house in 8 hours . his wife maggie can wash all the windows in 4 hours . how many hours will it take for both of them working together to wash all the windows ?
"work hrs = ab / ( a + b ) = 32 / 12 = 3 2 / 2 answer is c"
multiply(divide(const_60, add(divide(const_1, 8), divide(const_1, 4))), add(divide(const_1, 8), divide(const_1, 4)))