Standard Equation of a line is:
Where m is the slope and b is the y-intercept.
The first thing to do is find the slope. Recall the slope formula:
In this case we know that when the x variable has changed 1 unit, y has decreased by 1,200. So, the slope is:
We also need the y intercept. This is at x=0. We know that the car is originally worth 26,000 dollars so our y intercept is:
Plug it in to our standard equation to get:
The car will be worth $500 when so just set the equation equal to 500:
And solve for x.