For this, you can first find the annual decrease factor, like this
*You can express the percentage like this
*Then, for the annual decrease factor, you have
Now, the exponential decay is modeled by the equation
So, then the exponential function to find the population of the city after x years is
Then, the population after 5 years will be
Rounding, because there are no parts of people
Therefore, the population after 5 years of this city will be 291 people.