The condition gives you two equations T - B = 2, (1) (T+6)*(B+6) - T*B = 120. (2) Simplify eq(2): T*B + 6B + 6T + 36 - T*B = 120, 6B + 6T = 120 - 36 = 84, T + B == 14. Thus the modified system of equation is THIS: T - B = 2 (3) T + B = 14 (4) Add the equations (3) and (4). You will get 2T = 2 + 14 = 16. Hence, T = = 8. Then from (4), B = 14 - T = 14 - 8 = 6. Answer. Tom is 8 years old. His brother is 6 years old. Check. (8+6)*(6+6) - 8*6 = 120. ! Correct !