To rewrite the expression \( 5^3 \cdot 6^3 \) using a single base, we can observe that both terms are raised to the power of 3. This allows us to factor out the exponent:
\[ 5^3 \cdot 6^3 = (5 \cdot 6)^3 \]
Now, we can simplify the base:
\[ 5 \cdot 6 = 30 \]
So, the expression can be rewritten as:
\[ 5^3 \cdot 6^3 = 30^3 \]
Thus, \( 5^3 \cdot 6^3 = 30^3 \).