The previous population was 14000.
Explanation
The population decreased by 35% since the last measurement. So the current population is less than the previous population.
current population=9100
previous population =x
current population is 35% less than the previous population x
[tex]9100=x*(100-35)/100\\9100=(x*65)/100\\x=(100*9100)/65=14000[/tex]
The previous population was 14000.