Answer:
401 people per square mile
Step-by-step explanation:
First find the number of people per square mile in Detroit by dividing people by square miles:
672,800/142.9 = 4708.18754374
Then do the same for Grand Rapids:
195,100/45.3 = 4306.84326711
Subtract:
4708.2-4306.8 = 401.4
Round to the ones place:
401