The units for the volume are in cubic meters, or m^3. Think of a 1 m by 1 m by 1 m block, the volume of which is 1*1*1 = 1 m^3.
The diameter is 17 meters, half of which is 17/2 = 8.5 meters. So the radius is r = 8.5
In the second to last line, the '6's go on forever. It's only due to rounding is why that '7' shows up.
The answer above is approximate because pi = 3.14 is approximate. Use more decimal digits in pi to get a more accurate volume. However, your teacher wants you to use pi = 3.14
