Problem: jacob is 12 years old . he is 3 times as old as his brother . how old will jacob be when he is twice as old ?
Rationale: "j = 12 ; j = 3 b ; b = 12 / 3 = 4 ; twice as old so b = 4 ( now ) + ( 4 ) = 8 ; jacob is 12 + 4 = 16 answer : d"
annotated_formula: multiply(12, 3)