If my wife had a dollar for every time I made a sexist joke, she would have $0.77
Why do you say something so specific?
I made a math joke. I'm not sexist, I just think women should stay at home and are not cut out for real jobs and stuff.
When you immediately judge an entire gender as being mentally unfit to work in jobs, then other people will see that as the exact definition of sexism, so it doesn't help if you say you're not sexist.  There is no reason why women cannot work in jobs, but it is the widespread discrimination that they face that keeps them out of the workforce.  If you wouldn't want your sisters or daughters to end up in this situation, it is best to stop perpetuating these stereotypes.