Final answer:
If the measure of angle E is 42.3°, the measure of angle C will also be 42.3°.
Step-by-step explanation:
Vertical angles are pairs of angles that are formed by two intersecting lines. In a pair of vertical angles, the measure of one angle is equal to the measure of the other angle. Therefore, if the measure of angle E is 42.3°, the measure of angle C will also be 42.3°.