I'm having a hard time with significant figures. Any help would be appreciated.

Question

The first one is 0.0000000502. I put that it has three significant figures. Is this correct?

The other numbers I haven't a clue about are:
5.52
299,792,458
206,265

I get the jist of it, but I'm still struggling with the concept.

Answer 1

0.0000000502 = 3 sig. figures

5.52 = 3

299,792,458 = 9

206,265 = 6