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

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.