Answer:
A. 15
Explanation:
When a tangent and a secant, two secants, or two tangents intersect outside a circle then the measure of the angle formed is one-half the positive difference of the measures of the intercepted arcs.
Hence,
(2x + 15)° = 1/2[(10x + 20)° - 80°]
2(2x + 15)° = (10x - 60)°
4x + 30 = 10x - 60
60 + 30 = 10x - 4x
90 = 6x
90/6 = x
15 = x
x = 15