Perhaps you don't understand because you have neither read clearly nor copied the "question" correctly.
I think you probably mean y = (1/2)x + 2.
If so, this is a linear equation in slope-intercept form with slope = 1/2.
The graph will be a straight line from NE (Maine) to SW (Arizona) and will cross the y axis where y = 2.
Since 2 points determine a straight line, 2 points are sufficient to determine the equation of the line.
