Never begin adjusting or leveling the deck as your first course of action when you notice uneven cutting. The very first thing you need to do is to make certain that your tires are all inflated to the proper pressure. If that is not the answer to the issue, you will need to look to the owner's manual for checking and adjusting. If your deck is of the "fully suspended type". you have have lost a bolt or pin from one of the hanger bars. If your deck is of the trailing type that uses "gauge wheels", you may have a problem with one of the gauge wheels. Always check tire pressure first, then look for bent, worn, or missing parts, and finally as last resort.........you actually perform an adjustment procedure. Good luck