a can do a job in 9 days and b can do it in 27 days . a and b working together will finish twice the amount of work in - - - - - - - days ?
"1 / 9 + 1 / 27 = 3 / 27 = 1 / 9 9 / 1 = 9 * 2 = 18 days answer : b"
add(divide(const_1, 9), divide(const_1, 27))