Create a Summary Sheet, Continued 4. Delete Column C and D Select Column C and D. Go to Home->Cells->Delete. Click on Delete Sheet Columns.   What Do You See? The equations in the Revenue column now read: #REF!. The equation doesn’t have the data for Net and Quantity anymore. It has nothing to reference, hence the error message.   Go ahead: select those cells and hit the delete key to clear the busted equations. Home ->Cells -> Delete ->Delete Sheet Columns Exam 77-882: Microsoft Excel 2010 Core 5. Applying Formulas and Functions 5.3. Apply cell references in formulas: Troubleshoot a formula