#### Answer

Equation: y=-1000x+25000
The polar bears will by extinct by 2030

#### Work Step by Step

First our y-intercept is 25,000 because that is the number of polar bears we started with. Next our slope is -1000 because that is the rate at which the polar bears decline each year. So our equation is:
y=-1000x+25000
Now we can find the point at which the polar bears will go extinct by plugging in 0 for y since that is the number of polar bears remaining:
0=-1000x+25000 (subtract 25000 from both sides)
-25000=-1000x (divide by -1000 from both sides)
25=x
So the polar bears will be extinct in 25 years (2030)