Formula for linear growth is f(x) = mx+b
m is the slope or in this case the population growth/decline. x is the number of years and b is the original population.
in this case it will be p(t) = mt+b
lets find the population decline m.
In 1996 the population was 3200. This is a decline of 140 moose over 2 years. We need to know how many moose decline each year, so divide 140/2 and you get 70.
70 moose are declining each year. So m = 70, but it's declining so we need a negative. m = -70
So lets put it in the equation:
p(t) = -70t + b
So now it's easy to find b. We just plug in the year and population and get our b. Let's use 1996. The time has been 6 years from 1990 and the population in 1996 is 3200.
use the formula p(t) = -70(t) + b
t = 6
p(6) = 3200.
So p(6) = -70(6) + b = 3200
p(6) = -420 + b = 3200
-420 + b = 3200
b = 3620
Now you can plug in the years for t and get the decline in population.
We need the year 2009. So 2009-1990 = 19. Our t=19.
p(19) = -70(19) + 3620 = -1330 + 3620 = 2290.