"Where are you taking your dog?"
Translation:Ble dych chi'n mynd â'ch ci?
Yes, the second part of the sentence should agree with the first part and it should have read:-
Ble wyt ti'n mynd â dy gi?
However since this lesson is about comparison and this sentence is nothing to do with comparison it's now been replaced with a more suitable one.
Thanks for the comment and for bringing this to our attention.