Answer:
You count how many significant figures there are and because it's division you see which one has the least amount. 1.3 only has two significant figures so the answer will only have 2 sig figs. So, 21.3 divided by 1.3 equals 16.385 but the answer is 16 because you only include 2 sig figs because that's how many are in 1.3. 21.3/1.3=16
