Match up the sides for each triangle using the little marks through the sides
1 to 1, 2 to 2 and 3 to 3
When you do this you see that x corresponds to c on the first triangle.
The 3 angles in a triangle = 180.
Find c by subtracting A and B from 180
C = 180- 29-63 = 88
Now x = c so x = 88
The answer is C. 88