Right-click on the sheet tab and choose Delete from the pop-up menu.
You'll be warned that it's an undo-able operation; click OK if you're
sure you want to proceed. If you decide you really didn't want to
delete the sheet, you'll have to close the workbook without saving,
then reopen it.

As long as no formulas depend on cells on the sheets you're deleting,
you'll be fine.