WTF People. 13% This is SO basic and talked about SO often.
Actually that question is vaguely worded. Who has heard of a dual core processor in modern times?
They exist. But there is nothing vague at all. It's Windows Server 2016, the minimum is 16 cores to license, so the lowest number of packs of two is eight. Nothing vague.
Exist and exist in common use are two completely different things.
They are pretty common. but that's irrelevant. How does dual core procs being uncommon make the question any harder OR vague in any way?