Can you tell me what are you/what you are thinking about?
what you are
Who usually does/do the washing up?
does
Why didn't Bella come/not come to the party?
come
What did/were they arguing about?
were
Do you know where/where do John and Maria live?
where
Could you tell me how much this jacket costs/costs this jacket?
this jacket costs
How much far/far is it to the town centre?
far
Which do you prefer/you prefer – white or brown bread?
do you prefer