The given question is incomplete. The complete question is as follows.
Boxes A and B in the figure have masses of 13.4 kg. and 4.8 kg. , respectively. The two boxes are released from rest. What would be the speed of the boxes when box b has fallen a distance of 0.50 m? The coefficient of kinetic friction between box a and the surface it slides on is 0.20. Use conservation of energy.
Explanation:
Let us assume that box B is falling down, so equation of force for box B is as follows.
T =
.......... (1)
Now, force of equation for box A is as follows.


T =
........... (2)
We will equate both equation (1) and (2) as follows.
= 


a = 
= 1.1415 
Now, we will calculate the velocity of the box after falling through a distance of 0.50 m as follows.

= 
= 1.07 m/s
Thus, we can conclude that speed of the given boxes is 1.07 m/s.