If N is the population of the city and t is the time in years, then:

N(t) = N0e^(kt)

If the population decreased from 900,000 to 800,000 from 2003 to 2005 then:

N(0) = 900,000

N(2) = 800,000

t = 2 years

Therefore, solving for k we have:

N(2) = N0e^(2k)

800,000 = 900,000e^(2k)

900,000e^(2k) = 800,000

e^(2k) = 8/9

k = (1/2) ln(8/9)

k ≈ −0.059

Using the value of k above, the population in 2008 is:

N(5) = 900,000e^(5k)

N(5) = 900,000e^(5*−0.059)

N(5) ≈ 670,078

The population in 2008 will be approximately 670,078.