1. **State the problem:** We need to find the surface area (area) of a scalene triangle with base $b = 5$ cm and height $h = 9$ cm. 2. **Formula:** The area $A$ of a triangle is given by the formula: $$A = \frac{1}{2} \times b \times h$$ 3. **Substitute the values:** $$A = \frac{1}{2} \times 5 \times 9$$ 4. **Calculate:** $$A = \frac{1}{2} \times 45$$ 5. **Simplify:** $$A = \cancel{\frac{1}{2}} \times 45 = 22.5$$ 6. **Answer:** The surface area of the scalene triangle is $22.5$ square centimeters.