Answer:
Therefore the initial amount of animal was 89.
Step-by-step explanation:
Given that,at rate of 3.5% per year, the population of a certain animal species decreases.
The population growth formula:

A= number of population after n year.
P= initial population.
n= time in year
r= rate of growth per annum.
Here A=80, P=?, n= 3 years, r= -3.5% = -0.035[ since the rate of growth decrease]
Putting the all values,



≈89.
Therefore the amount of animal at its initial stage was 89.