Answer:
x = 9
Step-by-step explanation:
The triangle is split into two similar triangles. They have the same shape but not the same size. To solve, write a proportion.
[tex]\frac{9}{81}=\frac{3x-20}{3x+36}[/tex]
Cross multiply to solve for x.
9(3x+36) = 81(3x-20)
27x + 324 = 243x -1,620
1,944 = 216x
9 = x
