That adhd feel when you try to "show your work" with a math problem

My dad was born in 1946. I feel comfortable telling you this because it's not used in any of my bank security questions. Today at dinner I tried to figure out how old he is, and narrated my thought process out loud.

"So sixty years plus four because of the six in forty six plus eighteen because of the time since the millennium, so eighteen plus four is twenty two, and twenty two plus sixty is eighty two! Wait, no, he's definitely in his seventies. Okay, where did I fuck up? So sixty plus four for the six in forty six...oh, I tried to round forty six to an even number and rounded it to forty, meaning the gap between there and the millennium was sixty, but you don't round to forty you round to fifty, so fifty plus four plus eighteen, so he's...wait, okay--"

Meanwhile my husband is just sitting there like

 

I'm really good at math, I swear to god. One year I lost my graphing calculator and because I knew my parents couldn't afford to replace it I just did the logarithms and equations in my head the rest of the year. Pulled a C+, which feels decent to me considering. It's just that I got there via patches and workarounds equivalent to fixing your car engine with gum and pantyhose.