It is 12.2
Most schools wrongly teach you to always round a half up (so the answer would be 12.3) but, while this is a simple rule to teach, it is not really correct. Under this rule:
12.3
1860
It is: 12.4
The number is already rounded to exactly that degree.
The answer is 210,000,000
100
1860
It is: 12.4
The number is already rounded to exactly that degree.
The answer is 18.2
10
755.3
It is 1.01 when rounded to the nearest hundredth
7.3
0.1
342.8
0.3
1.0