Answer:
X=15
Step-by-step explanation:
line segment with length 18 is tangent and other one is secant so
[tex] {18}^{2} = 12(12 + x) \\ 324 = 144 + 12x \\ 324 - 144 = 12x \\ 180 = 12x \\ x = 180 \div 12 \\ x = 15[/tex]
