The answer is 5,852 deer.
The population density of deer in the county is 11 deer per square mile. This means that there are 11 deer in 1 square mile. So, there will be x deer in 532 square miles. Make the proportion:
11 deer : 1 square mile = x : 532 square miles
x = 11 deer * 532 square miles : 1 square mile
x = 5,852 deer