A new car worth 25000 is depreciating in value by $5000 per year

What are you trying to figure out here

y = 25,000 - 5,000x

x being the number of years, and y being the resulting price.

To find out when the car will be $5,000:

5000 = 25000 - 5000x

-20000 = - 5000x

x = 4

so in 4 years (hope this is what you were asking)