Problem: a and b can do a piece of work in 7 days , b and c in 8 days , c and a in 9 days . how long will c take to do it ?
Rationale: "2 c = 1 / 8 + 1 / 9 – 1 / 7 = 47 / 504 c = 47 / 1008 = > 1008 / 47 = 21.4 days the answer is c ."
annotated_formula: divide(multiply(7, const_3), subtract(divide(add(divide(multiply(7, const_3), 9), add(divide(multiply(7, const_3), 7), divide(multiply(7, const_3), 8))), const_2), divide(multiply(7, const_3), 7)))