Question

A wheel of mass M and radius R rolls on a level surface without slipping. If the angular velocity of the wheel about its center is ?, what is its linear momentum relative to the surface?

Answer 1

The most important thing you should remember in order to get how is its linear momentum relative to the surface is that the point on the circumference is moving at w rad/second. 
Therefore, here is the solving formulae:
if $v = R * w$ you can easily get  linear momentum p :
 $p = M * v = M * R * w$
I'm sure that helps.