Answer:
c
Step-by-step explanation:
Given a tangent- secant from an external point to the circle, then
The product of the external part and the entire secant is equal to the square of the tangent, that is
8(8 - 4 + 2x) = 12²
8(4 + 2x) = 144 ( divide both sides by 8 )
4 + 2x = 18 ( subtract 4 from both sides )
2x = 14 ( divide both sides by 2 )
x = 7
Thus
QS = 8 - 4 + 2x = 4 + 2x = 4 + 2(7) = 4 + 14 = 18 → c
