I believe the population exponential rule is P = (Po)e^(kt)

where Po = initial P

k = any rational number

t = time

So from 2003 to 2005,

t = 2 years

Po = 800,000

P = 700,000

k = ?

700,000 = 800,000e^(k*2)

e^(2k) = 700,000 /800,000 = 7/8

2k *ln(e) = ln(7/8)

k = ln(7/8) /2

k = -0.066766

Then, from 2003 to 2007,

t = 4 years

Po = 800,000

P =?

k = -0.066766

Can you solve for P now?

You should get P = 612,500