Problem: if the side length of square b is three times that of square a , the area of square b is how many times the area of square a ?
Rationale: "let x be the side length of square a . then the area of square a is x ^ 2 . the area of square b is ( 3 x ) ^ 2 = 9 x ^ 2 . the answer is a ."
annotated_formula: multiply(const_4, const_4)