ANSWER
x = 12
EXPLANATION
By the intersecting chords theorem, the product of each segment of one chord equals to the product of each segment of the other chord:
[tex]15\cdot8=10x[/tex]
Solving for x:
[tex]\begin{gathered} 120=10x \\ x=\frac{120}{10} \\ x=12 \end{gathered}[/tex]
