For the first scenario, you’re looking at a compound interest problem. You’re given all the information you need, so just input it into the compound interest equation.
A = P(1 + r/n)^nt
P is your principal, aka starting amount. That’s the 12000 people you start with.
R is your rate of interest, aka how much your principal is expanding by. That’s the 5% growth rate each year, or 0.05.
N is the number of times your principal grows each year. That’s only once here.
T is however long the change lasts. In this scenario, its from 2006 to 2020, so 14 years.
Input all this in and solve for A, which is your total amount.
A = 12,000(1 x 0.05/1)^(1 x 14) = 23,759.18
Since I doubt you can have 1/5 of a person, you round this down to 23,759, which is your answer.
I’d like to help with your second problem, but it’s cut off on the edge of the image, I can’t see all the numbers.