1. **State the problem:** We need to find the ratio of pencils to erasers in a pencil box that contains 8 pencils and 4 erasers. 2. **Formula for ratio:** The ratio of two quantities $A$ and $B$ is given by $\frac{A}{B}$. 3. **Apply the formula:** Here, the ratio of pencils to erasers is $\frac{8}{4}$. 4. **Simplify the ratio:** Divide numerator and denominator by their greatest common divisor (GCD), which is 4. $$\frac{8 \div 4}{4 \div 4} = \frac{2}{1}$$ 5. **Interpretation:** The ratio of pencils to erasers is $2:1$, meaning there are 2 pencils for every 1 eraser. **Final answer:** The ratio of pencils to erasers is $2:1$.