Your answer is 3277 because a negative divided by a negitive makes it a positive.
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

The previous population was 14000.
A variable next to any number means to multiply, so we would do the inverse operation -- We would divide 0.48 by 0.6, which is 0.8. Therefore, W=0.48. To check your work, multiply 0.6 by 0.8, and what do you know? It's 0.48! :)