The less bulky group (iso-propyl) is at the equatorial position and (tert-butyl) is at the axial position. Thus, the trans-conformation is more stable.

The bulkier group (tert-butyl) is at the equatorial position and (iso-propyl) is also at the equatorial position. Thus, the cis-conformation is more stable.

The bulkier group (tert-butyl) is at the equatorial position and (iso-propyl) is at the axial position. Thus, the cis-conformation is more stable.

The bulkier group (tert-butyl) is at the axial position and (iso-propyl) is also at the axial position. Thus, the cis-conformation is more stable.