First set up a proportion because they are similar triangles:
9/3x-20 = (72+9)/(56+3x-20)
9/3x-20 = 81/3x+36
9(3x+36) = 81(3x-20)
27x+324 = 243x-1620
1944 = 216x
x = 9
We need to divide

So, we can divide each terms of the numerator by 3p. So,

=
\frac{2}{3p} [/tex] cannot be further simplify. So, the final answer is: