Answer:
a. 27.5°
Step-by-step explanation:
You want the measure of external angle U formed by tangent UR and secant US, given ∠S = 24° and arc RS = 103°.
Inscribed angle
The inscribed angle RST is half the measure of the intercepted arc RT, so ...
arc RT = 2·∠S = 2·24° = 48°
External angle
External angle U is half the difference of the intercepted arcs.
∠U = (arc RS -arc RT)/2 = (103° -48°)/2 = 55°/2
∠U = 27.5° . . . . choice A
