1. **Problem statement:** We need to calculate the lateral surface area (mantelyta) of a cylindrical energy drink can with height $h=12$ cm and radius $r=3$ cm. 2. **Formula:** The lateral surface area of a cylinder is given by the formula: $$A = 2\pi r h$$ where $r$ is the radius and $h$ is the height. 3. **Substitute the values:** $$A = 2 \pi \times 3 \times 12$$ 4. **Calculate:** $$A = 2 \pi \times 36 = 72 \pi$$ 5. **Approximate using $\pi \approx 3.14$:** $$A \approx 72 \times 3.14 = 226.08$$ 6. **Round to whole square centimeters:** $$A \approx 226$$ **Final answer:** The lateral surface area of the can is approximately 226 square centimeters.