3x + y = 48 (1) (x is the weight of the box of gaming machines) 3x + 5y = 72 (2) (y is the weight of the box of DVDs) ------------------------- Subtract equation (1) from equation (2) (both sides). You will get 4y = 72 - 48 = 24 ====> y == 6. Thus the the weight of the box of DVDs is 6 pounds. From this point, can you complete the solution on your own ?