The population is decreasing by 15% every year
The initial population = 15,000
Since it decreases every year
Decreases every year = (100 - 15)
The rate of the population every year = 75%
What this simply means is that the population of California keep decreasing by 15%
Assuming the population of California in 2018 is 15000
By 2019 , it would have decreased by 15%
The new population in 2019 will now be = (100 - 15)% x 15000
= 85% x 15000
= 0.85 x 15000
= 12, 750
Therefore, the population in 2019 will now be 12, 750.... It will keep decreasing like that