To see how these fractions are equal, I divided the numerators by the denominators. For instance, you could have 4 over 5 (4/5) and divide 4 by 5 (4/5) to get 0.8. Now you'll do the same thing for the fractions given
24/45=0.533...
8/15=0.533...
48/90=0.533...
5/9=0.5556
As you can see, the only fraction that doesn't equal 0.53, or the outlier, is 5/9 or 0.5556