1. **State the problem:** We need to find the volume of a prism with length 36 mm and a triangular cross-section with base 18 mm and height 29 mm. 2. **Formula for volume of a prism:** $$\text{Volume} = \text{Area of cross-section} \times \text{Length}$$ 3. **Formula for area of a triangle:** $$\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}$$ 4. **Calculate the area of the triangular cross-section:** $$\text{Area} = \frac{1}{2} \times 18 \times 29 = 9 \times 29 = 261 \text{ mm}^2$$ 5. **Calculate the volume of the prism:** $$\text{Volume} = 261 \times 36 = 9396 \text{ mm}^3$$ 6. **Answer:** The volume of the prism is **9396 mm³**.