find the average of first 4 multiples of 15 ?
"average = ( 15 + 30 + 45 + 60 ) / 4 = 37.5 answer is e"
divide(add(add(add(4, const_1), add(add(4, const_1), const_2)), add(subtract(15, 4), subtract(15, const_2))), 4)