Answer:
x = 12
Step-by-step explanation:
By property of intersecting secants outside of a circle:
[tex]x \times 15 = 20 \times 12 \\ x = \frac{20 \times 12}{15} \\ x = \frac{20 \times 3}{5} \\ x = 4 \times 3 \\ x = 12[/tex]
