You can do anything to a fraction as long as you do it to the numerator and the denominator and the fraction will still represent the same amount, so let's make 4.5 fifths into a clearer number by multiplying the numerator and denominator by 2.
\({4.5 \over 5} = {{4.5 \cdot 2} \over {5 \cdot 2}} = {9 \over 10}\)
ANSWER:
in fraction form: \(9 \over 10\)
in decimal form: \(0.9\)
in percent form: \(90%\)%
I hope this is helpful,
Catarina