100 feet
To find the total length of the entire string you multiply 8 times 5 and get 40.
To convert into feet multiply by 3 and get 120 feet.
To find the total amount of string he uses, multiply 4 times 5 and get 20. It is already in feet.
Next you subtract 120 - 20 and get 100 feet, the total amount of string he has left.
There would be 18 books per box.
126/7 = 18
Hope this helps!
For the $3.75 it would cost $281.25 and for the $3.95 it would cost $296.25
Hope this helps!
The common denominator is 2
