You can just use the law of tangents, then subtract the two values.
What did you get?. Let's see if we jive.
Here's a diagram
So I solved the problem and I wanted someone else to do it to see if my answers are correct before I turned this in. A passenger in an airplane flying at an altitude of 10km sees two towns directly to the east of the plane. The angles of depression to the town are 28 degrees and 55 degrees. How far apart are the towns? could you please include hypotenuese lengths.