Answer:
x is 12
Step-by-step explanation:
» From scalar properties:
[tex]{ \tt{ \frac{FG}{FH} = \frac{AB}{AC} }} \\ \\ { \tt{ \frac{9}{6} = \frac{18}{x} }} \\ \\ { \tt{x = \frac{18 \times 6}{9} }} \\ \\ { \boxed{ \tt{ \: x = 12 \: }}}[/tex]
