Substituents on cyclohexane can, in principle, occupy either axial or equatorial positions. However, in general, equatorial substituents are more preferred since they are more stable because of reduced steric interactions.
In the images below, the 1,3-diaxial interaction can be highlighted and contrasted between both conformers. This interaction is a steric interaction between axial groups on "1" and "3" carbons, which leads to destabilization of that conformation, dependent on the size of the groups.
The larger the alkyl substituent is, the greater the preference for the equatorial position since the larger the group the greater the steric interaction with the axial hydrogens. The more stable compound on the left would be much more common.