J - G = 12 (1) (the difference of their ages) J + G = 84 (2) (the sum of their ages) ------------------------------------------------------Add the two equations 2J = 12 + 84 = 96 ====> J = 96/2 = 48. Then from eq(2) G = 84 - 48 = 36. Answer. 48 and 36 years.