1. The problem is to solve a simple algebraic equation suitable for grade 7 level: Solve for $x$ in the equation $$3x + 5 = 20$$. 2. The formula used here is to isolate the variable $x$ by performing inverse operations. Important rules: addition and subtraction undo each other, multiplication and division undo each other. 3. Start by subtracting 5 from both sides to get rid of the constant term on the left: $$3x + 5 - \cancel{5} = 20 - \cancel{5}$$ which simplifies to $$3x = 15$$. 4. Next, divide both sides by 3 to solve for $x$: $$\frac{3x}{\cancel{3}} = \frac{15}{\cancel{3}}$$ which simplifies to $$x = 5$$. 5. So, the solution to the equation is $x = 5$. This means when $x$ is 5, the original equation holds true. This is a basic algebra problem teaching how to isolate variables using inverse operations.