1. **State the problem:** Solve the equation $X + 3 = 1$ for $X$. 2. **Formula and rules:** To isolate $X$, subtract 3 from both sides of the equation. This uses the rule that you can perform the same operation on both sides of an equation without changing its equality. 3. **Intermediate work:** $$X + 3 = 1$$ Subtract 3 from both sides: $$X + 3 - \cancel{3} = 1 - \cancel{3}$$ 4. **Simplify:** $$X = 1 - 3$$ $$X = -2$$ 5. **Answer:** The solution to the equation is $X = -2$. This means the vertical line at $x = -2$ matches the solution.