how many positive integers less than 5,000 are evenly divisible by neither 18 nor 21 ?
"integers less than 5000 divisible by 18 5000 / 18 = 333 . something , so 333 integers less than 5000 divisible by 21 5000 / 21 = 238 . # # , so 238 we have double counted some , so take lcm of 18 and 21 = 105 and divide by 5000 , we get 47 . so all numbers divisible by 18 and 21 = 333 + 238 - 47 = 524 now subtract that from 4999 . 4999 - 524 = 4428 answer d ."
divide(factorial(subtract(add(const_4, 18), const_1)), multiply(factorial(18), factorial(subtract(const_4, const_1))))