The angle of depression from an airplane to the top of an air traffic control tower is 56 degrees. If the tower is 320 feet tall and the airplane is flying at an altitude of 7,450 feet, how far away is the airplane from the tower?
Here is a video to explaing angle of depression and angle of elevation to you.
It is good. You should watch it.
And here is your diagram. You should work out the hight the plane is above the tower first.
You do not need any angles or trig for that :)
Think about what I have already given you and try and answer the question yourself.
You can always add another response to ask more questions if you get stuck.