When mary was born, she weighed 8 pounds. when she was 10 years old, she weighed 10 times as much. how much more did mary weigh when she was 10 years old than she was born?

She weighed 72 pounds more when she was ten years old than when she was born.

10×8=80
80-8=72
8 in the second equation equals how much she weighed when she was born, the 80 equals how much she weighed at 10.
subtract those to find how much more she weighed at 10 years old than at birth.