To estimate the number of hats each shelter will receive from the total of 1,596 hats distributed equally among 4 shelters, we want to round 1,596 to the nearest hundred for easier calculation. The closest hundred is 1,600.
Therefore, the best equation to use for estimating the number of hats each shelter will receive is:
\[ 1,600 ÷ 4 = h \]
So the correct response is: 1,600 ÷ 4 = h.