Problem: find the average of first 3 multiples of 5 ?
Rationale: "average = ( 5 + 10 + 15 ) / 3 = 10 answer is a"
annotated_formula: divide(add(add(add(3, const_1), add(add(3, const_1), const_2)), add(subtract(5, 3), subtract(5, const_2))), 3)