So we have 5 hours and 20 min which is equal to 5 and 20/60 hours, or 5 and 1/3 hours. We also have 2 hours and 45 min which is equal to 2 and 45/60 hours or 2 and 3/4 hours.
Our fractions are
5 and 1/3 = 16/3
2 and 3/4 = 11/4
Problem: 16/3 - 11/4
Find common denominators: 64/12 - 33/12
Subtract: 31/12
Your answer is 31/12 hours, which is 24/12 + 7/12 hours = 2 and 7/12 hours.
Since 1/12 hour = 5 min, your final answer is 2 hours and 35 minutes.