Check my answer, please.

We have this

A =  Beginning Amount  (  1  -  rate of decay)^t

Where  the  beginning amount is   0.65 kilograms

And the rate of decay  = 8%  =  .08.....so we have

A  =  0.65 ( 1  - .08)^t

A  = 0.65 ( .92)^t

So.....the rate of decay  is  8%   ⇒  A