find the average of all prime numbers between 20 and 30
"prime numbers between 20 and 30 are 23,29 required average = ( 23 + 29 ) / 2 = 52 / 2 = 26 answer is e"
divide(add(add(add(20, const_1), add(add(20, const_1), const_2)), add(subtract(30, 20), subtract(30, const_2))), 20)