We have to write 5.12 in fraction form.
As we have two decimals, we start with 512/100 and see if we can simplify it:
We divide both numerator and denominator by the same number (in this case, by the factor 2, two times, so in fact we are dividing by 4).
The fraction 128/25 is irreductible, so it is the simplest fraction form of 5.12.
The answer is 128/25.