f(6) = ?
Find 6 on the x axis and go up until you find the line. In this case, there's a point at (6, 3), so f(6) = 3.
f(x) = ?
Here, it's just asking for the equation of the line. You have two points: (6, 3) and (0, -2). (-2 - 3) / (0 - 6) = -5 / -6 = 5/6. So, the slope is 5/6. The y-intercept is -2, so f(x) = 5/6y - 2.
