Playing golf with clients is one way to 'mix business with pleasure'. [=to do something enjoyable that is related to your work]
I accidentally 'mixed up' the two files. [=I put each of the files in the place where the other one should have gone]
He 'got mixed up in' a plan to destroy the government. [=he became involved in a plan to destroy the government]
(..) Get those bellows working. Go! Bilbo! Up there. On my mark... ...pull that lever. Balin! Can you still mix a flash-flame? Aye. It'll only take a jiffy. Come on! We don't have a jiffy. Where's the sulfur? You sure you know what... ...you're doing? (..)2013 The Hobbit: The Desolation of Smaug
(..) Cutting it off.. How did you know it would work? I didn't. Now I'm just a liability. This prick stands right in the mix, while seven or eight of them turn Zeke all at the same time. Is that how you tweaked your leg? No, shit's been bugging me a while. Got no time for his lucky ass. (..)2013 World War Z
(..) How did you all escape this? The expenditure of ammunition. Is that how you tweaked your leg? No, shit's been bugging me a while. This prick stands right in the mix, while seven or eight of them turn Zeke all at the same time. But they got no time for OI' Dirty Bastard here. (..)2013 World War Z