Okay all we have to do is get them to have the same denominator, which in this case we will use first. Then we will order them:
5/8 = 2.5/4
3/4 (Already has 4 as its denominator.)
1/2 = 2/4
9/16= 2.25/4
Sooo, the order is clear: 1/2, 9/16,5/8,3/4.
Hope this helps and have a great day.