The tension in the rope must be the same at the end of both boxes.

Let the blue box have a mass of and let the orange box have a mass of

Doing a FB analysis on the blue box [the x direction is what matters] , we see that

:

Doing a FB analysis on the orange box [the x direction is what matters] , we see that

:

Therefore, since the tensions are the same, we see that

Can you take it from here?

--Chris