Answer:
2.88%
Explanation:
This gives us a pair of simple equations:
100% = 520(1)
x% = 15(2)
By simply dividing equation 1 by equation 2 and taking note of the fact that both of equations have the same unit (%); we have

Taking the inverse (or reciprocal) of both sides yields

-> x = 2.88%
Therefore, 15 is 2.88% of 520