1. **Problem statement:** Calculate the volume of a cylinder (walec) with radius $r=5$ cm and height $h=7$ cm. 2. **Formula for the volume of a cylinder:** $$V = \pi r^2 h$$ This formula comes from the fact that a cylinder is a prism with a circular base, so its volume is the area of the base times the height. 3. **Calculate the volume:** $$V = \pi \times 5^2 \times 7 = \pi \times 25 \times 7 = 175\pi$$ 4. **Approximate the volume:** Using $\pi \approx 3.1416$, $$V \approx 175 \times 3.1416 = 549.78$$ 5. **Answer:** The volume of the cylinder is approximately $549.78$ cubic centimeters. This completes the solution for the first question about the cylinder volume.