Answer
At d=-2, which means 2 decades before the finches population started increasing, the population was 20.
At d=0, which means that the initial population of finches was 45.
At d=1, which means after 1 decade, the population of finches was 67 finches.
Work Step by Step
P(d)=45$\times$$1.5^{d}$
P(-2)=45$\times$$1.5^{-2}$
=$\frac{45}{1.5^{2}}$ = $\frac{45}{2.25}$ = 20
P(0)=45$\times$$1.5^{0}$ = 45 $\times$ 1 = 45
P(1)=45$\times$$1.5^{1}$ = 45 $\times$ 1.5 = 67.5 so 67 finches as you can't have half of a finch.
