Since those triangles are similar, the ratio between their corresponding sides must be equal. From this statement, we have the following equation for x:
[tex]\frac{x}{10}=\frac{12}{6}[/tex]
Solving for x:
[tex]\begin{gathered} \frac{x}{10}=\frac{12}{6} \\ x=\frac{12}{6}\times10 \\ x=2\times10 \\ x=20 \end{gathered}[/tex]
The length of x is equal to 20. The answer is option D.
