Answer:
[tex]x=30[/tex]
Step-by-step explanation:
Both triangles in this figure are similar. Therefore, we can set up the following proportion:
[tex]\frac{21}{x}=\frac{14}{20}[/tex].
Cross-multiply to solve:
[tex]14x=21\cdot 20,\\x=\frac{21\cdot20}{14},\\x=\fbox{$30$}[/tex].
