49.5 (0.82) ^x

What is the rate of change? I know it is decay already.

Just checking to make sure I know it is right.

You are correct in stating you have a decay. This is because the base of the exponential 0.82 is in the form 1+r where 1+r = 0.82 solves to r = - 0.18

The negative r value means we have decay.

The rate of decay is 18% since 0.18 = 18/100 = 18%

For example, if we started with 100 items then after 1 unit in time, you'd have 82 items since 100-18 = 82