1. **State the problem:** Solve for $x$ in the equation $3x = 243$. 2. **Understand the equation:** The equation means $3$ multiplied by $x$ equals $243$. 3. **Isolate $x$:** To find $x$, divide both sides of the equation by $3$ to undo the multiplication. 4. **Perform the division:** $$x = \frac{243}{3}$$ 5. **Calculate the result:** $$x = 81$$ 6. **Conclusion:** The value of $x$ that satisfies the equation $3x = 243$ is $81$.