We know the lengths of the adjacent and opposite sides when looking at the angle x, so we use those two sides to find the trig ratio.
So we use Opposite/adjacent (Tangent) Which is 54/72=0.75
Now we get out the trig ratio table. Because we used the tangent ratio (O/A) , we use that column to look for the closest number to 0.75. The closest is 0.754, and the degree for it is 37 degrees