1. **Problem:** Solve the equation $x + b = a$ for $x$. 2. **Formula:** To isolate $x$, subtract $b$ from both sides. 3. **Work:** $$x + b = a$$ Subtract $b$: $$x + \cancel{b} - \cancel{b} = a - b$$ $$x = a - b$$ 4. **Explanation:** We moved $b$ to the right side by subtracting it from both sides, isolating $x$. **Final answer:** $x = a - b$