1. Let's start with a simple algebra problem suitable for Year 7 students. 2. Problem: Solve for $x$ in the equation $$2x + 5 = 15$$. 3. Formula and rules: To solve for $x$, we need to isolate $x$ on one side of the equation. We do this by performing inverse operations. 4. Step 1: Subtract 5 from both sides to get rid of the constant term on the left. $$2x + 5 - 5 = 15 - 5$$ $$2x = 10$$ 5. Step 2: Divide both sides by 2 to solve for $x$. $$\frac{2x}{2} = \frac{10}{2}$$ $$x = 5$$ 6. Explanation: We used subtraction to remove the constant term and division to isolate the variable. This is a basic principle in solving linear equations. 7. Final answer: $$x = 5$$