To solve for \( f(g(3)) \), we first need to find \( g(3) \) using the set \( g \).
The set \( g = {(2,4), (3,6), (5,1)} \) contains pairs of values. We can see that:
- \( g(3) = 6 \)
Now, we need to find \( f(6) \) using the set \( s \).
The set \( s = {(1,3), (4,5), (5,6), (6,0)} \) again contains pairs. We look for the pair where the first element is \( 6 \):
- \( s(6) = 0 \)
Thus, \( f(g(3)) = f(6) = 0 \).
The final answer is:
\[ \boxed{0} \]