1. Let's start with a basic algebra question suitable for UP Police SI exam preparation. 2. Problem: Solve for $x$ in the equation $$2x + 5 = 15$$. 3. Formula: To solve a linear equation, isolate the variable $x$ by performing inverse operations. 4. Step 1: Subtract 5 from both sides: $$2x + 5 - 5 = 15 - 5$$ $$2x = 10$$ 5. Step 2: Divide both sides by 2 to solve for $x$: $$\frac{\cancel{2}x}{\cancel{2}} = \frac{10}{2}$$ $$x = 5$$ 6. Final answer: $x = 5$. This is a straightforward linear equation solving method, which is commonly tested in exams.