From Mechanics

First find the angle, \displaystyle \alpha , between the impulse and the initial velocity.

\displaystyle \begin{align} & \tan \alpha =\frac{12}{24} \\ &\\ & \alpha =26\textrm{.}6{}^\circ \end{align}

Then subtract this from \displaystyle {{90}^{\circ }} to get the angle between the initial velocity and the wall.

\displaystyle \text{Angle =}90-26\textrm{.}6={{63\textrm{.}4}^{\circ }}