two pipes a and b can separately fill a tank in 16 and 18 minutes respectively . a third pipe c can drain off 45 liters of water per minute . if all the pipes are opened , the tank can be filled in 18 minutes . what is the capacity of the tank ?
"1 / 16 + 1 / 18 - 1 / x = 1 / 18 x = 16 16 * 45 = 720 answer : b"
multiply(multiply(inverse(subtract(add(add(divide(const_1, 16), divide(const_1, 18)), divide(const_1, 45)), divide(const_1, 18))), const_3), 18)