Answer is 1 foot 9 inches difference
Step by step
First we will change both measurements to feet and inches
3 ft 9 inches and 5 ft 6 inches ( 1/2 ft is half of 12 = 6)
Subtract
5 ft 6 inches
-3 ft 9 inches
Since 1 foot is 12 inches we will borrow 12 inches from 5 foot so we can subtract, add 12 to 6 and subtract 1 from 5
4 ft 18 inches
-3 ft 9 inches
__________
1 ft 9 inches difference
Problem solved