Answer:
63%
Explanation:
You would have to set up a proportion.
so 504 of 800 = x of 100 is what you are trying to figure out.
504 x
____ = ____
800 100
To solve this logically, to get from 800 to 100 you need to divide by 8, so in order to keep with the proportion you would also have to divide 504 by 8, which results in x being 63. (Or 63%)
Shortcut: The shortcut I use when the numbers are a bit harder to work with is the cross multiply and then divide method. First you multiply the numbers that are diagonal from each other, in this case those numbers would be 504 and 100 which would result as 50,400. Then you would divide by the remaining number (800). With this method you would also arrive at x = 63. This method is just a bit quicker when it come to bigger numbers in my opinion.