"Де ти ідеш/їдеш?"
"Де ви ідете/їдете?"
"Куди ти ідеш/їдеш?"
"Куди ви ідете/їдеш?"
Is йдете just an alternate spelling of ідете or do the two words have slightly different meanings?
It's the same thing as with і/й conjuctions. The meaning is the same, there are two spellings for euphony
The hint says to use де, and then marks де as incorrect. I've lost 3 hearts this lesson because Duo is being so unclear about whether куди or де is appropriate.