I think theres no simplest form because 12 is even and 57 is odd and you can not simplify a fraction with a odd and even number.
57/100 is already in its simplest form
-57
38/57 = 2/3
69
4/19
12/57 can be simplified to 4/19
It is: 0.57 = 57/100
4/19
12/19 or 0.6316
19 over 4
57/215 is in its simplest form.
It is 11 and 2/5 as a mixed number in its simplest form