A wheel of diameter of 68.0 cm slows down uniformly from 8.40 m/s to rest over a distance of 115 m. How long does it take for the wheel to come to the stop?

I would divide 8.40 into 115 this will give the Seconds, Slow down uniformly is not a measurement. Plus the wheel is measured by seconds, not RPM?
If you multiply 8.40 X 3.14(circumference)this will give the distance moved in 1 revolution.