I seem to get stuck on these....

Find a linear equation in the formP=mt+b(y=mx+b), which gives the population,P,tyears from 2010.

Answer: P(y) = 20x + 1500

Show your work here:

20 represents the growth rate

X represents the number of years (t)

B represents the initial population for 2010

Is this right? And then.....

Use your equation in part b to approximate the population in the year 2030.

Answer:Population 1900 in the year 2030

Show your work here:

P(y) = 20x + 1500 x = 20

P(y) = 400 + 1500

P(y) = 1900

Finally... and this is where I get stuck.....

Use your equation in part b to approximate how many years it will take the population to reach 7000.

Any help will be greatly appreciated