I have a Mac Book Air and have purchased individually numbers and pages. I was given an excel file on a thumb drive and cannot open it. Is there a way to open the xcl file in numbers?

Excel does not use the .xcl extension for any of its native file formats? The only files I've ever seen with xcl as the file extension were associated with embedded application code projects.

If this is in fact an Excel file, but an encrypted one, you cannot open it (in excel or any compatible application) without the decryption password.

Numbers supports excel, if you're having an issue opening perhaps it isn't an excel file. It should be .xls or .xlsx if isn't one of those two document types then it isn't an excel spreadsheet.