"What city bus goes to the center?"
Translation:Яка маршрутка їде у центр?
і and й can be used interchangeably as conjunctions and in the beginning of some words for euphony. But їде starts in ї (not i), so it's not the case. Іде and йде are the forms of a word іти, їде is a form of їхати. Іти is usually used when you move your feet, їхати - when you use some kind of vehicle. Іти can also be used to talk about routes of vehicles