1. **State the problem:** Solve for $y$ in the equation $X = y + 7$. 2. **Formula and rules:** To isolate $y$, subtract 7 from both sides of the equation. 3. **Intermediate work:** $$X = y + 7$$ Subtract 7 from both sides: $$X - \cancel{7} = y + \cancel{7} - 7$$ 4. **Simplify:** $$y = X - 7$$ 5. **Explanation:** We moved 7 to the left side by subtracting it, which isolates $y$ on the right side. This gives the solution for $y$ in terms of $X$. **Final answer:** $$y = X - 7$$