(y^12)/5
9/45=1/5
x^5/x^5=1
y^16/y^4=y^12
I believe the first and last one are polynomials. Usually they start with the highest exponent first and then work their way down.
You have to multiply by 16's and then divide the two numbers
To express a decimal number (with a finite decimal expression) in a fraction, you work like this: the numerator is the number without decimale separator (you simply pretend it's not there), while the denominator will be
, where n is the number of digits after the decimal separator.
So, in your case, the number without decimal separator is 53, and you have two digits after the decimal separator, so the fraction will be
which is irreducible.