1. The problem is to find the value of $x$ in the equation $3x + 5 = 20$. 2. We use the basic algebraic principle of isolating the variable $x$ by performing inverse operations. 3. First, subtract 5 from both sides: $$3x + 5 - 5 = 20 - 5$$ which simplifies to $$3x = 15$$ 4. Next, divide both sides by 3 to solve for $x$: $$\frac{3x}{3} = \frac{15}{3}$$ Using cancellation notation: $$\frac{\cancel{3}x}{\cancel{3}} = \frac{15}{3}$$ which simplifies to $$x = 5$$ 5. Therefore, the solution to the equation is $x = 5$.