39º
1) Considering what's been given we can sketch this out:
From these trees leaning on each other, we can visualize a triangle (in black).
2) So now, since we need to find the other angle, then we need to apply the Law of Sines to find out the missing angle:

As we need the measure of the angle, (not any leg) then we need to use the arcsine of that quotient:

3) Hence, the approximate measure of that angle X is 39º