Answer:
GH = 15
Explanation:
given a tangent and a secant drawn from an external point to the circle, then the product of the secant's external part and the entire secant is equal to the square of the measure of the tangent , that is
FG × FH = EF²
12(12 + 2x - 1) = 18²
12(11 + 2x) = 324 ( divide both sides by 12 )
11 + 2x = 27 ( subtract 11 from both sides )
2x = 16 ( divide both sides by 2 )
x = 8
Then
GH = 2x - 1 = 2(8) - 1 = 16 - 1 = 15