Most stable conformation of cyclohexane is chair form. Substituents at equatorial positions are most stable.
At C-1, methyl group is at equatorial position and down the plane. At C-4, it must be up the plane and the position again is equatorial. So the above conformation is most stable. But if at C-1, methyl group is present at axial which is up the plane, at C-4, it should be down the plane which again is axial. So this is less stable conformation. To get stability ring flip will occur and both the axial groups will go the equatorial positions. So the equilibrium constant of the ring flipping will be grerater than 1.
