Answer:
3/4 inches
Step-by-step explanation:
Subtract Jimmys string length from Sam's string length
7 1/2 - 6 3/4
Get a common denominator of 4
7 1/2*2/2 - 6 3/4
7 2/4 - 6 3/4
Borrow 1 ( or 4/4) from the 7
6 4/4 + 2/4 - 6 3/4
6 6/4 - 6 3/4
3/4
(8)(-4.5) is not equivalent because 8 times -4.5 results in negative value