1. **Restate the problem:** You want to understand why $a - c = (a - b) + (b - c)$ and how it works with numbers. 2. **Explain the formula:** The expression means the difference between $a$ and $c$ can be split into two parts: the difference between $a$ and $b$, plus the difference between $b$ and $c$. 3. **Use the given values:** Let $a = 5$, $b = 3$, and $c = 1$. 4. **Calculate each difference:** $$a - b = 5 - 3 = 2$$ $$b - c = 3 - 1 = 2$$ 5. **Add the differences:** $$(a - b) + (b - c) = 2 + 2 = 4$$ 6. **Calculate $a - c$ directly:** $$a - c = 5 - 1 = 4$$ 7. **Compare results:** Both methods give the same result, $4$, so the formula holds true. 8. **Summary:** The difference between $a$ and $c$ is the sum of the differences between $a$ and $b$ and between $b$ and $c$. This is because subtraction is like moving along a number line step by step.