Problem: if 9 a - b = 10 b + 70 = - 12 b - 2 a , what is the value of 9 a - 11 b ?
Rationale: "this implies 9 a - b = 10 b + 70 , 9 a - b = - 12 b - 2 a , 10 b + 70 = - 12 b - 2 a manipulating the second equation gives us 9 a - b = 10 b + 70 = = > 9 a - 11 b = 70 answer is b"
annotated_formula: multiply(negate(multiply(divide(70, 2), 2)), 9)