It takes harry 38s to walk from x1 = -14m to x2 = -52m . what is his velocity?

Initial distance from which Harry starts to walk (x1) = - 14 meter
Final distance up to which Harry walks (x2) = - 52 meter
Time taken by Harry to walk from x1 to x2 = 38 second
Then
Velocity = (x2 - x1)/Time taken
             = [- 52 - (-14)]/38 meter/second
             = (-52 + 14)/38
             = -(38/38) meter/second
             = -1 meter/second.
So the velocity at which Harry walks is -1 meter per second. Hope you are satisfied with the procedure and the procedure is also clear enough for you.

The earths atmosphere is made up of nitrogen and oxygensolids turning into gases is called sublimation.