Answer:
arc ABD = 56°
Step-by-step explanation:
The measure of arc EF is the same as the measure of central angle ECF. That angle is a vertical angle with angle ACB, so they are congruent. The angle sum theorem tells you the measure of angle ACD is the sum of the measures of angles ACB and BCD. That sum is 35° +21° = 56°.
Since the central angle ACD has measure 56°, arc AD has measure 56°.
