The trick here is to recognize that you can represent the years as single-digit numbers. For example, let 1 on the horiz. axis represent the year 2001, and let 6 represent 2006. Can you now plot (1,8.7) [which represents 8.7% in the year 2001) and (6,10.8)? Draw a straight line thru these points.
Next, determine the slope of this line. Are you familiar with the slope formula?
It has various forms, all representing "rise over run."
Apparently the slope, "m," is 0.75.
Next, determine the coordinates of the y-intercept (the point at which your line crosses the vertical (or y-) axis. That's the y-intercept, "b," or 5.45.
Then subst. your results into the "slope-intercept form of the equation of a straight line, which is y=mx + b. Result: y = 0.75x + 5.45.
