[tex]\begin{gathered} \frac{x+6}{3x}\div\frac{x^2-36}{3x-18} \\ \frac{x+6}{3x}\times\frac{3x-18}{x^2-36} \\ \end{gathered}[/tex]
then
[tex]\begin{gathered} \frac{x+6}{3x}\times\frac{3(x-6)}{(x+6)(x-6)} \\ \frac{x+6}{3x}\times\frac{3}{x+6} \\ \frac{(x+6)\times3}{3x\times(x+6)} \\ \frac{3}{3x} \\ \frac{1}{x} \end{gathered}[/tex]
answer: 1/x
