how many multiples of 5 are there between 10 and 89 , 10 and 89 inclusive ?
"5 multiples are . . . 10,15 , 20,25 , 30,35 , 40,45 , 50,55 , 60,65 , 70,75 , 80,85 , . . . , . . . , the answer is = 16 answer is b"
add(divide(subtract(89, 10), 5), const_1)