1. **State the problem:** Solve for $x$ in the equation $3x + 5 = 20$. 2. **Formula and rules:** To solve a linear equation, isolate the variable $x$ by performing inverse operations. 3. **Step 1:** Subtract 5 from both sides to get rid of the constant term on the left: $$3x + 5 - 5 = 20 - 5$$ which simplifies to $$3x = 15$$ 4. **Step 2:** Divide both sides by 3 to isolate $x$: $$\frac{3x}{3} = \frac{15}{3}$$ which simplifies to $$x = 5$$ 5. **Final answer:** $x = 5$