|Math hard! CREDIT.|
It's actually pretty common for people to just write in a lower total and avoid writing in a tip. They might suck at math, but they're still smart enough to not call themselves out on that shit. Had this person just written in $11.00 we never would have assumed their shortcomings. Perhaps they were in a hurry. Perhaps they wanted to test my own math abilities. But I certainly wouldn't assume they are a dumbass. Thanks for clearing that up for me.
And Lamebook is awesome. Go there.