Question

AC is tangent to circle O at A. If mBY =24, what is m

Answer 1

The correct question in the attached figure

we know that
the inscribed angle measures half of the arc it comprises.
then
m∠YAB=(1/2)*m∠BY-------------> m∠YAB=(1/2)*24°=12°
m∠YAC=90°-m∠YAB=90°-12°=78°

the answer is the option C) 78°