Is "y" a time in hours or a speed in revolutions per hour? Or both?
A wheel of diameter x inches has a circumference of \(\displaystyle \pi x\) inches so \(\displaystyle \frac{\pi x}{12}\) feet. If it is making y revolutions per hour it will travel \(\displaystyle \frac{\pi xy}{12}\) feet per hour so a total of \(\displaystyle \frac{\pi xy^2}{12}\) feet in y hours.