I car on a slope....
The centripetal force, (mv^2)/r , acts horizontally away from the centre of the bank. The component weight of the car down the slope is mgsin(x).
For the car to not slide up or down the track, this force mgsin(x), must be equally balance by another force which happens to be the component of the centripetal force up the track.
So, mgsin(x) = (mv^2)*cos(x)/r
Then the masses cancel and you can rearrange for the angle, x.
The beauty of this is no matter if you are driving a (frictionless) tractor or riding a bicycle, as long as you are travelling at the critical velocity, you will not slip.