The choice of which is x and which is y is up to you, but normally you see "time" as the x-axis. If you use this convention, then "life-expectancy in years" would be your y-axis.
From these choices, P1=(2000, 76.1) and P2 = (2007, 78.2). From these two points you can calculate the slope m. Do you know how to do that?
Then when you have the slope, you use either of the above points and create the point-slope form of a linear equation,