Let's factor the expression step by step! 🎉 **Step 1:** Look at the expression: $x^2 - 3^3$ **Step 2:** Calculate $3^3$: it's $3 \times 3 \times 3 = 27$ **Step 3:** Now the expression is $x^2 - 27$ **Step 4:** This is a difference of squares because $27 = 9 \times 3$, but 27 is not a perfect square. So we can't use difference of squares directly. **Step 5:** The expression $x^2 - 27$ is already simplified and cannot be factored further using simple methods. So, the answer is: $$x^2 - 27$$ Great job! Keep practicing! 🌟