ΔDEF rotates 90° clockwise about point A to create ΔD 'E 'F. Therefore, which equation must be true? m∠DEF = m∠D 'F 'E '

The equation that is given does not have to be true, because the letters are not in the same order. Therefore, we are not comparing the corresponding pairs of angles. They may or may not be congruent.

When a shape is rotated, the corresponding pairs of angles are congruent.