To convert grams to kilograms, move the decimal to the left three places. For example, the box that's 4,180 grams, it would become 4.18 kilograms. The question wants you to convert the weight of the boxes to kilograms, and then it wants you to multiply $6.43 by the weight of each box to find out how much he spends. So, do 4.18 times 6.43, and then .82 by 5.43, and then add the two answers you get! Hope that helps, let me know if you need more help solving~