welk/welke=wich. Wich one of the two you should use, is something you have to feel.
examples: Met welke auto reed je? (wich car did you drive?)
In welk huis woonde je? (in wich house did you live?)
In the spoken language, welk/welke, usually, can be replaced by 'wat' of 'wat voor'.
example: Met wat voor auto rijd je? (what car do you drive?)
wie=who