There are 4 tests to check whether two triangles are congruent or not.
(courtesy of learnhive.net)
1. Prove that the two triangles are congruent.
Out of the 4 congruence tests, the best to use is ASA, although the side is not an included side. Therefore:
2. Find the value of x given that .
First of all, we know that and .
Now, we know that .
Hence, we can solve x algebraically: