1. **State the problem:** Solve the equation $a + b + 20 = 60$ for $a + b$. 2. **Identify the goal:** We want to find the value of $a + b$. 3. **Use algebraic manipulation:** Subtract 20 from both sides of the equation to isolate $a + b$. 4. **Perform the subtraction:** $$a + b + 20 - 20 = 60 - 20$$ $$a + b = 40$$ 5. **Conclusion:** The sum of $a$ and $b$ is 40.