Well, Since every 1 person throws away 4.5 × 10² g trash each day (365 days in each year), You would times 3.2×1063.2×106 by the 4.5 × 10² g to get how much trash was thrown away each day and then times that by 365 to figure how much trash was thrown away the entire year
9 divided by 72 = 0.125 0.125 is the weight of one book 0.125 times 80 = 10kg. So 80 books weight 10kg. 72 divided by 9 = 8 books make up 1 kg. 8 times 6 =48