Answer:
Population = 1378.1994 residents
Step-by-step explanation:
The current population (t = 0) is 31,000 residents, the following year (t = 1), you have:
Population = 31000 (1 / (1 + 1)) +1200 = 16700
For the year t = 2
Population = 16700 (1 / (2 + 1)) +1200 = 5375
For the year t = 3
Population = 5375 (1 / (3 + 1)) +1200 = 2275. Successively it is found that for t = 7
Population = 1425,595 (1 / (7 + 1)) +1200 = 1378.1994