If you are proving a congruence of triangles then you need to match the corresponding parts to the triangle you are proving congruent.
BAC would then be congruent to MJR because of the corresponding angles
B is the same angle as M
A is the same angle as J
C is the same angle as R
It's a half of an equilateral triangle because their angles measure 30° and 60° (an equilateral triangle has 3 angles of 60°)
So x=(2h/√3)/2=h√3=27√3≈15.6
The answer to your question is 3/8.
