Answer:
[tex]x=10[/tex]
Step-by-step explanation:
Set up a proportion with corresponding sides. The two sides marked with a small line in them represent that those sides are equal. Therefore, the side marked 30 is broken into two lines of equal length (each 15).
Thus, we can set up the following proportion:
[tex]\frac{x}{20}=\frac{15}{30},\\\\30x=300,\\\\x=\boxed{10}[/tex]
