1. **Stating the problem:** Find the lateral surface area (L.S.A) of a trapezoidal prism. L.S.A = P \times h, where P is the perimeter of the base and h is the height of the prism. 2. **Identify given values:** - Top base of trapezoid = 15 m - Bottom base of trapezoid = 5 m - Left side = 10 m - Right side = 10 m - Height of trapezoid (not needed for perimeter) = 7 m - Height of prism = 6 m 3. **Calculate the perimeter (P) of the trapezoid base:** $$P = 15 + 5 + 10 + 10 = 40 \text{ m}$$ 4. **Calculate the lateral surface area (L.S.A):** $$\text{L.S.A} = P \times h = 40 \times 6 = 240 \text{ m}^2$$ **Final answer:** The lateral surface area of the prism is **240 m²**.