Answer:
[tex]\Large \boxed{\sf x=9}[/tex]
Step-by-step explanation:
A transversal that is parallel to a side in a triangle defines a new smaller triangle that is similar to the bigger triangle.
[tex]\displaystyle \frac{9+72}{9} =\frac{3x-20+56}{3x-20}[/tex]
Solve for x
[tex](9+72)\times(3x-20)=(3x-20+56)\times(9)[/tex]
[tex]243x-1620=27x+324[/tex]
[tex]216x=1944[/tex]
[tex]x=9[/tex]
