Problem: what is the sum of the multiples of 7 from 77 to 91 , inclusive ?
Rationale: "the formula we want to use in this type of problem is this : average * total numbers = sum first , find the average by taking the sum of the f + l number and divide it by 2 : a = ( f + l ) / 2 second , find the total numbers in our range by dividing our f and l numbers by 7 and add 1 . ( 91 / 7 ) - ( 77 / 7 ) + 1 = 3 multiply these together so what we show average * total numbers = sum ( 91 + 77 ) / 2 * 3 = sum 84 * 3 = 252 e"
annotated_formula: multiply(divide(add(subtract(91, const_3), add(77, const_2)), const_2), add(divide(subtract(subtract(91, const_3), add(77, const_2)), 7), const_1))