81.2 = 812/10 or 406/5 in fraction
812 is an integer and not a fraction. There is no sensible way to express it as a fraction.
812/100
812 is an integer and there is no simpler form.
812 is an integer, not a fraction. There is not really a sensible way of writing it as a fraction. However, if you must, you can use (812*k)/k where k is any non-zero integer as an equivalent fraction.
If you mean 8/12 then it is 2/3 simplified
It is 3 and 812/1000. This can be simplified if you so wish.
2/3
812/100 or 203/25
0.812 = 812/1000 = 203/250
12/15 is different.
Assuming that is 90.222... with the 2 recurring, then: 90.222... = 90 2/9 = 812/9
0.812 is a fraction. It is a fraction in decimal form rather than in the form of a ratio. However, that does not stop it being a fraction. Its rational equivalent is 812/1000 which can be simplified. But simplification could mean that you could lose information about the precision of the fraction.