1. **Problem:** Find the area of the trapezoid with bases 24.3 cm and 9.7 cm, and height 8.5 cm. 2. **Formula:** The area $A$ of a trapezoid is given by $$A = \frac{1}{2} (b_1 + b_2) h$$ where $b_1$ and $b_2$ are the lengths of the two bases and $h$ is the height. 3. **Substitute values:** $$A = \frac{1}{2} (24.3 + 9.7) \times 8.5$$ 4. **Calculate sum of bases:** $$24.3 + 9.7 = 34$$ 5. **Calculate area:** $$A = \frac{1}{2} \times 34 \times 8.5 = 17 \times 8.5$$ 6. **Multiply:** $$A = 144.5$$ 7. **Answer:** The area of the trapezoid is $144.5$ cm$^2$.