assuming this is linear
write everything in thousands smaller
p=mx+b
b=initial amount
m=growth rate
city increases by 4 each year
in 2025, population is 450
find it after 2010, with 2010 being year 0 or x=0
so
2025-2010=15 years
15*4=60
increased by 60
450=result=increase+originalin2010
increase=60
450=60+original
minus 60
390=original
p=4x+390