Make the bottom number (the denominator) the same, so that it should be easier to see which one is larger.
4 and 8 are both multiples of 8, so you can make the bottom number 8 by multiplying 4 by 2, and 8 by 1 (because it's already 8).
So that means you get 4/8 (because 2 times 2 is 4, and 4 times 2 is 8) and 5/8 (because 5 times 1 is 5 and 8 times 1 is 8).
So now that the fractions have the same bottom number, you can compare them easily.
The answer is 5/8, because now that the fractions are comparable, we can see that 5 is bigger than 4. :)
