To solve the equation
\[ 3 - 5 \cdot 3^x = 18, \]
first, isolate the term involving \( x \):
\[ -5 \cdot 3^x = 18 - 3. \]
This simplifies to:
\[ -5 \cdot 3^x = 15. \]
Now, divide both sides by -5:
\[ 3^x = -\frac{15}{5} = -3. \]
Since \( 3^x \) (an exponential function) is always positive for real numbers, there is no real solution to the equation \( 3^x = -3 \).
Thus, the final answer is:
No real solution.