To solve the equation \( \frac{3 - 5}{3x} = 18 \), we first simplify the left side.
\[ 3 - 5 = -2 \]
So the equation becomes:
\[ \frac{-2}{3x} = 18 \]
Next, we can cross-multiply to eliminate the fraction:
\[ -2 = 18 \cdot 3x \]
This simplifies to:
\[ -2 = 54x \]
Now, we can isolate \( x \) by dividing both sides by 54:
\[ x = \frac{-2}{54} \]
Simplifying further:
\[ x = \frac{-1}{27} \]
Thus, the final answer is:
\[ x = -\frac{1}{27} \]