# Thread: Reversing an equation... stuck!

1. ## Reversing an equation... stuck!

I seem to get stuck on these....

Find a linear equation in the form P = mt + b (y = mx + b), which gives the population, P, t years 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

2. $7000 = 20x + 1500$

Solve for x

3. why is that so simple? Yet I can't see it???