File shortcut opens wrong Excel version

I have Office 2016, but occasionally need Word 2003, so I also have Office 2003 installed. If I click a shortcut to an XLSX file, it opens in Excel 2003 rather than Excel 2016, and wants to save itself to a new file with an arbitrary number. Is there any way I can:
a) Make the shortcut always lead to Excel 2016?
b) Disable or uninstall Excel 2003 while still being able to use Word 2003?

I'm using Windows 10 Pro x64.

I had already set Excel 16 as default program "for all files it can open/" But I had not also set "Associate File Type with a Program." Turns out, XLSX was assigned to something like "Microsoft compatibility converter." I guess the system assumed that if I wanted XLSX files to open in that, then I wasn't planning to open them in Excel 2016.

Problem now solved. Thanks.