If ΔXYZ≅ΔDEF, then what corresponding angle is congruent to angle X? (Enter your answer using the angle letter only.)

the corresponding angle congruent to angle X is angle D

Answer: Angle D

The order of the letters is very important when you write a congruence equation like what is shown. In this case, triangle XYZ is congruent to triangle DEF. We have X and D as the first letters of each respective letter sequence. The two angles X and D correspond, and therefore must be congruent. The corresponding parts of congruent triangles must be congruent themselves. This is like saying two houses are identical so the front doors must be the same also.

Note: Your book may use the acronym CPCTC which stands for Corresponding Parts of Congruent Triangles are Congruent.