1. **Stating the problem:** We need to solve the equation or expression given by the user. Since no specific problem was provided, let's assume a common algebra problem for a Secondary 3 student: Solve for $x$ in the equation $$2x + 5 = 15$$. 2. **Formula and rules:** To solve linear equations like this, we use the rule that whatever we do to one side of the equation, we must do to the other side to keep it balanced. 3. **Step-by-step solution:** - Start with the equation: $$2x + 5 = 15$$ - Subtract 5 from both sides to isolate the term with $x$: $$2x + 5 - 5 = 15 - 5$$ - Simplify both sides: $$2x = 10$$ - Divide both sides by 2 to solve for $x$: $$\frac{2x}{2} = \frac{10}{2}$$ - Simplify: $$x = 5$$ 4. **Explanation:** We first removed the constant term 5 by subtracting it from both sides. Then, since $x$ was multiplied by 2, we divided both sides by 2 to get $x$ alone. The solution is $x = 5$. **Final answer:** $$x = 5$$