find the average of first 4 multiples of 5 ?
"average = ( 5 + 10 + 15 + 20 ) / 4 = 12.5 answer is c"
divide(add(add(add(4, const_1), add(add(4, const_1), const_2)), add(subtract(5, 4), subtract(5, const_2))), 4)