Algebra 1... please help me?

A light plane flew from its home base to an airport 255 miles away. With a head wind, the trip took 1.7 hours. The return trip with a tail wind took 1.5 hours. Find the average airspeed of the plane and the average windspeed.

this involves system of equations. use substitution or elimination & please show work (:

1st trip speed = 255mi / 1.7hrs

1st trip speed = 150 mph

2nd trip speed = 255mi / 1.5hrs

2nd trip speed = 170 mph

average speed = (150mph + 170mph) / 2

average speed = 320 / 2

average speed = 160 mph