Respuesta :

The angle formed by the intersection of tangent and secant outside the circle equals half the difference of the intercepted arcs.

[tex] \frac{10x+20-80}{2}=2x+15 \\ 10x-60=2(2x+15) \\ 10x-60= 4x+30 \\ 10x-4x=30+60 \\ 6x=90 \\ x=90/6 \\ x=15[/tex]