1 pound= 16 ounces
STEP 1:
convert each weight given to ounces only; multiply each pound by 16 ounces per pound, then add the additional ounces each item weighs
Math Book:
= (2 pounds * 16 ounces/lb) + 13 ounces
= 32 + 13
= 45 ounces
Science Book:
= (1 pound * 16 ounces/lb) + 15 ounces
= 16 + 15
= 31 ounces
Backpack:
= (1 pound * 16 ounces/lb) + 1 ounce
= 16 + 1
= 17 ounces
STEP 2:
total the number of ounces of each item in step 1
= 45 oz math book + 31 oz science book + 17 oz backpack
= 93 ounces total
ANSWER: The total weight of the backpack and two books is 93 ounces.
Hope this helps! :)