Libre Office tries to open documents in Safari

Just loaded Libre Office on a Mac (OS High Sierra). I created a spreadsheet, saved as XLS. I try to open that document, and it tries to open in Safari; I get a message that Safari cannot open that kind of document. ?? What have I done wrong, and how can I fix it?

It seems your file associations for MS Office spreadsheets are incorrect. See Q33/A33 in Tutorial - Mac FAQ for a likely solution.

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