Question 21474
The answer is:
7' (6+ 3/4)" - 5' (11 + 5/16)"

a foot is 12', so change expression to this:

6' (18 + 3/4)" - 5' (11 + 5/16)"

change 3/4 to 12/16
subtracting term by term, the answer is:
1' (7 + 7/16)"