In the figure shown block B moves down with a velocity 10 m/s. The velocity of A in the position shown is

If B moves down at 10m/s . Therefore length of the string between A and the pulley is decreasing at a rate of 20m/s

$$\begin{gathered} V_A\cos 37=20m/s \\ {V}_A=\frac{20}{\cos 37}=25m/s \end{gathered}$$