Answer:
B. 28.1
Step-by-step explanation:
By the property of intersecting secant and tangent out side of the circle.
[tex]20 \times (20 + x) = {31}^{2} \\ 20(20 + x) = 961 \\ 20 + x = \frac{961}{20} \\ 20 + x = 48.05 \\ x = 48.05 - 20 \\ x = 28.05 \\ \huge \red{ \boxed{x = 28.1}}[/tex]
