let's say in 2006, year 0, there were "I" amount of customers, and we dunno what "I" is.
now, 4 years later in 2010, t = 4, there are 900 skaters, and the rate of decrease is 5%.
[tex]\bf \qquad \textit{Amount for Exponential Decay}\\\\
A=I(1 - r)^t\qquad
\begin{cases}
A=\textit{accumulated amount}\to &900\\
I=\textit{initial amount}\\
r=rate\to 5\%\to \frac{5}{100}\to &0.05\\
t=\textit{elapsed time}\to &4\\
\end{cases}
\\\\\\
900=I(1-0.05)^4\implies 900=I(0.95)^4\implies \cfrac{900}{0.95^4}=I
\\\\\\
1105\approx I\qquad thus\qquad \boxed{A=1105(0.95)^t}[/tex]
[tex]\bf \\\\
-------------------------------\\\\
\textit{now in 2006, 4 years earlier, year 0, t = 0}
\\\\\\
A=1105(0.95)^0\implies A=1105\cdot 1\implies A=1105[/tex]
