how many numbers from 10 to 50 are exactly divisible by 9 ?
"10 / 9 = 1 and 50 / 9 = 5 = = > 5 - 1 = 4 . therefore 4 answer : e"
add(divide(subtract(multiply(floor(divide(50, 9)), 9), multiply(add(floor(divide(10, 9)), const_1), 9)), 9), const_1)