1. **State the problem:** We have a parallelogram with an area of 40 units squared, a height of 5 units, and an unknown base $b$. We need to find the value of $b$. 2. **Formula for the area of a parallelogram:** $$\text{Area} = \text{base} \times \text{height}$$ This means: $$A = b \times h$$ where $A$ is the area, $b$ is the base, and $h$ is the height. 3. **Plug in the known values:** $$40 = b \times 5$$ 4. **Solve for $b$:** Divide both sides by 5: $$\frac{40}{\cancel{5}} = b \times \frac{\cancel{5}}{5}$$ which simplifies to: $$8 = b$$ 5. **Answer:** The missing base $b$ is 8 units. This means the base length that makes the area 40 with a height of 5 is 8 units.