a no-brainer is an obvious decision that doesn’t need any thought. A: Should I go to summer school this summer or go stay with my dad in Florida? B: Dude, that’s a no-brainer...

👍Борис
«Ну ты спросил/спрашиваешь!»

To me, Boris’s translation means “everybody knows this” and that’s not what no-brained means to me.