find the average of all the numbers between 40 and 80 which are divisible by 3 .
"sol . average = ( 42 + 45 + 48 + 51 + 54 + 57 + 60 + 63 + 66 + 69 + 72 + 75 + 78 / 13 ) = 780 / 5 = 60 . answer d"
divide(add(add(40, const_4), subtract(80, const_4)), const_2)