Pick the closest whole number to 8.6 that is not a fraction. In this case it is 9.
9000
10000000
100
It is 0 0.00005
The answer is 400 but these websites on related links are good.
Round 12 to 1 significant figure is 10.
7000
0.1
9000
2,000,000
10000000
It is 0.01
0.9
12
800
100
200