Are you trying to open an XLR file? XLR file type is a an extension for spreadsheet files (or chart files) used by Microsoft Works suite.
Microsoft Works is a discontinued office suite created by Microsoft.
How to open an XLR File on your Mac:
See also: How to open Mac’s .pages file format on Microsoft Windows
1-Locate the .xlr file
2-You cannot open this file. Double click to open it. You will see this message saying: There is no application set to open the “document .xlr”
3-The easist way to open this file is to change .xlr to .xls extension.
To do this, simply select the file by clicking
Then, press return (or enter). Now enter the new extension name, .xls.
You will be prompted this message saying: Are you sure you want to change the extension from “.xlr” to “.xls”? Simply select Use .xls.
Now simply open this new file. Preview will open this file.
Alternatively you may want to download and install an app. For instance, Open Office can open .xlr files.