How do you do this problem?

55°

Step-by-step explanation:

In the triangle towards the bottom-left, we can see that it is an iscosceles triangle, which means that the two angles opposite of those two sides are also equal. Along with this, a triangle will also only have 180° for the sum of all of its angles.

When you put another x in the angle next to the 37°, you get an equation similar to:

x in this case will then be 55 degrees.

ca = ec

cpctc makes it so that corresponding parts of the triangle you proved to be equal are equal, the other options aren't part of the part of the triangles you proved to be equal.