Question

an airplane travels 4000m in 16 seconds on a heading of 35 whats is its velocity

Answer 1

In the question, you just gave a complete and detailed
description of the plane's velocity vector:

       4,000/16  meters/second , heading 35 degrees .

You might want to simplify the speed and make it a unit rate,
but otherwise, it's perfect.

         250 meters/second, heading 35 degrees .