Lorentz Velocity Transformations

Object A is moving in the x direction at velocity $v_{\scriptscriptstyle A}$ in the rest frame of observer S. Observer S' is moving in the x direction at velocity u relative to observer S. Derive a formula for the velocity $v_{\scriptscriptstyle A}'$ of object A in the rest frame of observer S'.

(Hint: Differentiate the Lorentz transformations for time t and position x.)