Cac du ma khong biet 

Vietnamese saying. Literally translates to "penis motherfucker don't know", but is used like "Fuck, I don't know this."

Person 1: *sees some math shit* "Yo, do you know this?"
Person 2: *sees it* "Cac du ma khong biet."

Cac du ma khong biet by CAC DU MA KHONG BIET June 4, 2018