How do I convert XLSX to XLS?

Answer 1

From the menu, click SAVE AS....

in the dialog, there is a FILE NAME and FILE TYPE combo box

select the FILE TYPE dialog and choose *.XLS

that will save the spreadsheet as a older version

Answer 2

With the spreadsheet file open, click the menu in upper left corner, then hover over "Save As". Select "Excel 97-2003 Workbook" to go to the older version.