Question

I need help I dont quite understand how to do it and if I did it correctly. Will give huge credit to whoever can give me a full explanation.

Answer 1

There's a theorem for this scenario that says the average of the measures of arcs AC and BD is equal to the measure of the angle formed by the chords AB and CD. In particular,

90° = 1/2 (arc AC + arc BD)

90° = 1/2 (arc AC + 126°)

90° = 1/2 arc AC + 63°

1/2 arc AC = 27

arc AC = 54°