A certain quantity decays exponentially over time. The initial quantity at t = 0 is 25,000. The quantity decays at a rate of 5%. What is the quantity at t = 3?

In order to sole the problem you need to create an equation to model what you are trying to do.

You end up with an equation looking like

25000*0.95^t

25000 is the starting value when t=0

95% is the amount remaining after the 5% decay

0.95 is being raised to the power of t to determine how many times it has decayed

When t=3 the equation should be

25000*0.95^3=21434.375