I have a MacBook 5,5 (Mid 2009).What software can I upgrade to from 10.11?

I'm not familiar with a MacBook model 5.5 (2009), but I did find a MacBook Pro Model 5,5 (2009). Assuming the MacBook Pro Model 5,5 is your computer, then El Capitain (10.11.6) is the latest OS your machine can handle. Sierra requires a MacBook Pro from 2010 or later. Here is the El Capitain combo updater, should you need to use it.

There isn't any such thing as a MacBook5,5. If you mean MacBook5,2 or MacBookPro5,5, they can't be upgraded past El Capitan.

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