Alt plus = sign for excel

Hello I am taking a Microsoft 365 course and for a quick SUM on Excel you use Alt and = sign

and looked up the equivalent for my Mac, though having to constantly look up the equivalent for mac keyboard in any other shortcut is annoying so I bought an external keyboard all the keys seem to function except for the Alt

if someone knows how to get the stubborn Mac to let me use the bloody Alt key I’d very much appreciate it.

thanks