Well, I will say things like "I'm a bit thick at maths" but obviously I can work out things like..err, yeah, 20% of whatever given number! I say it because I have never been confident in my ability in maths - I remember even feeling that way in infant school - and I think it is very probable that that's because I'm a girl.
But then, yeah, you meet people who don't even seem to know their 'times tables' and people that can't even do simple subtractions without getting their phone (calculator) out and you think...
But THEN, most of the people I come across who are like that are females. You never hear boys saying things like "oof, I'm retarded at maths". I don't mean to sound like this terrible feminist conspiracy theorist but it's completely true that school subjects are gendered and maths is for BOYS. And although boys will rarely say things like "ooh, I'm so thick at English, me", it's much more of a girlie quality to be articulate, to have a wide vocabulary etc (and, of course, studies suggest boys are socialised into more boisterous, confident personalities: girls think they're bad at maths through their OWN fault, boys are unphased by a lack of flair in English cos they don't think it's a "proper" subject)
God, I might not like maths but I love sociology, me!