1. Let's state the problem: Find the value of $x$ in the equation $$3x + 5 = 20$$. 2. The formula used here is to isolate $x$ by performing inverse operations. Important rules: addition and subtraction undo each other, multiplication and division undo each other. 3. Subtract 5 from both sides: $$3x + 5 - 5 = 20 - 5$$ $$3x = 15$$ 4. Divide both sides by 3 to solve for $x$: $$\frac{\cancel{3}x}{\cancel{3}} = \frac{15}{3}$$ $$x = 5$$ 5. So, the solution is $x = 5$. This means when $x$ is 5, the equation balances correctly.