Askateboarder with a mass of 45 kilograms is riding on a skateboard with a mass of 2.5 kilograms. what should be the velocity of the skateboarder if she has to attain a momentum of 264 kilogram meters/second? . blaaah

So momentum is just velocity times mass, this means Momentum = Velocity x Mass.
We can rearrange this to be Velocity = Momentum/Mass.

Since we know momentum and mass we can now solve.

Velocity = 264/(45+2.5)
              = 5.56 m/s