Help me with this math equation please

im not exactly sure how to do this one but i think that you can use pythagoras theorem which is a^2 +b^2=c^2. In the question you can use d^2 +e^2= f^2

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.

what is the question you are asking?