The easiest way to compare these numbers is to put them all over the same denominator.
If both the top and bottom of a fraction are multiplied or divided by the same divisor, the fraction will stay the same; ie 1/2 - multiplying both top and bottom by 2 gives 2/4 which is the same thing.
Look for the lowest common multiple of 8 and 20 (or, do a cheat which i do - multiply 8 by 20 to get an answer which is a common multiple)
This answer is 160.
Next, multiply the top of the fraction which had the 8 below it, by 20, and the top of the fraction with 20 below it, by 8.
This can now be simplified to
This can now be compared , to see that the
(note, > means the left is bigger than the right. < means the left is smaller than the right. This can be remembered by 2 ends is more than 1 end, so the bigger number will have the most ends.)