Martha is carrying her biology, science, and math textbooks. Her books weigh a total of 9 pounds. Her biology textbook weighs 3 pounds and her math textbook weighs 40 ounces. How many ounces does her science textbook weigh?

Answer=56 ounces

First lets find a conversion equation for pounds to ounces ...

1pound=16ounces

9pounds=9*16=144ounces

3pounds=3*16=48ounces

Given the data, the following equation can be made, where x is equal to the weight of her science textbook.

144=48+40+x

144=88+x

subtract 88 from both sides

56ounces=x

The science textbook weighs 56ounces

9 times 16 is 144 and 3 times 16 is 48. SO, 144-48 = 96 96-40 = 56 Her science textbook is 56 oz