if 12 men or 20 women can do a piece of work in 54 days , then in how many days can 9 men and 21 women together do the work ?
"b 30 days given that 12 m = 20 w = > 3 m = 5 w 9 men + 21 women = 15 women + 21 women = 36 women 20 women can do the work in 54 days . so , 36 women can do it in ( 20 * 54 ) / 36 = 30 days ."
inverse(add(divide(9, multiply(12, 54)), divide(21, multiply(20, 54))))