Help me with this question what is the units

In the diagram of circle o, what is the measure of zabc?

What adds to be the bottom number but also multiplies to be the top number with 8 on the bottom and 15 on top

Which statement explains how you could use coordinate geometry to prove the opposite sides of a quadrilateral are congruent? a. use the slope formula to prove the slopes of the opposite sides are the same. b. use the slope formula to prove the slopes of the opposite sides are opposite reciprocals. c. use the distance formula to prove the lengths of the opposite sides are the same. d. use the distance formula to prove the midpoints of the opposite sides are the same.