Question

What is the size of ∠ ABC shown in the above figure

Answer 1

∠ABC and ∠AOC share the same intercepted arc.  ∠AOC is a central angle, so the angle measure equals the intercepted arc, so the measure of arc AC=70

m∠ABC = 1/2(measure of arc AC)
m∠ABC = 1/2(70)
m∠ABC = 35°
(inscribed angle formula)

Answer 2

A. thirty-five degrees