If you place 10 packages per box, each box will weigh 10(3 lb 4 oz). This is 30 lb 40 oz. For 4 boxes you would have 4(30 lb 40 oz). This is 120 lb 160 oz. To put you answer in the correct form you need to change the 160 oz to pounds and ounces. 16 oz is equal to 1 pound, so divide 160 by 16. The 160 oz is equivalent to 10 lbs. Therefore the total weight of 4 boxes is 120 + 10 which equals 130 lb