Answer: In 2030, the population will be 16,800 and in 2040 the population will be 18,816.
Step-by-step explanation: To find the population in 2030, we need to calculate one decade of growth from 2020 to 2030:
Population in 2030 = 15,000 x (1 + 0.12)^1 = 16,800
Therefore, the population in Gastonia is expected to be 16,800 in 2030.
To find the population in 2040, we need to calculate two decades of growth from 2020 to 2040:
Population in 2040 = 15,000 x (1 + 0.12)^2 = 18,816
Therefore, the population in Gastonia is expected to be 18,816 in 2040.