In the equation y=mx+b, m=slope of the line and b=y-intercept. From the graph, we know the y-intercept is 4 so we can write y=mx+4. To find the slope: (0-4)/(-2-0) = (-4)/(-2) = 2. We can replace the m with 2 to get the final equation of y=2x+4 which is also the third answer.
