If the figures are similar, use a proportion to find the missing side?

Given:
The figure is
Find-:
The value of "x"
Explanation-:
The ratio of sides is
Compared with angle sides is
[tex]\frac{28}{21}=\frac{8}{6}=\frac{30}{x}[/tex]So, the value of "x" is
[tex]\begin{gathered} \frac{8}{6}=\frac{30}{x} \\ \\ x=\frac{30}{8}\times6 \\ \\ x=\frac{30}{4}\times3 \\ \\ x=\frac{15}{2}\times3 \\ \\ x=\frac{45}{2} \\ \\ x=22.5 \end{gathered}[/tex]The value of "x" is 22.5