Answer:
20,000
Explanation:
I'm assuming your class is using this model of the exponential decay function:
f(x) = a(1 - r)^x
In this case, the equation would be:
f(x) = 20,000(1 - .15)^x
or, when 1 - r is calculated:
f(x) = 20,000(.85)^x
The "a" value is basically the starting value, because on a graph, the starting value would be where x = 0. Anything to the 0th power is 1, and anything multiplied by 1 is the same thing, making "a" the same as the starting value, or the y-intercept.
Therefore, a = 20,000.
Hope this helps!