1. **State the problem:** Solve the equation $4x = 20$ using a bar model. 2. **Understand the equation:** The equation $4x = 20$ means four equal parts (each of size $x$) add up to 20. 3. **Bar model explanation:** Imagine a bar divided into 4 equal parts, each part representing $x$. The total length of the bar is 20. 4. **Formula used:** To find $x$, divide both sides of the equation by 4: $$4x = 20$$ Divide both sides by 4: $$\cancel{4}x = \frac{20}{\cancel{4}}$$ Simplifies to: $$x = 5$$ 5. **Interpretation:** Each small rectangle (each $x$) is equal to 5. 6. **Final answer:** $$\boxed{5}$$