To begin, you are given two point that this function would intercept: (0,3) where the 0 is the original year (2000) and 3 is the amount of million cars sold. The next point would be (6,2.5) Where the 6 is the 6 years later and the 2.5 is the 2.5 million cars sold. Since we have 2 points, we can work out the gradient by finding the rate of change in y and dividing by the rate of change in x:
We then substitute in the points:
Because we started on the y-intercept of (0,3), we already have our intercept value of 3. If we did not start with the y-intercept given, we could substitute in a point to solve for it: