So let's start with the slope-intercept form of a linear equation. That is y = mx+b where m is slope and b is the y intercept. But, this is an inequality. So first we have to look at the way the graph is shaded. Since it is shaded upwards, you know that it is in the form of y ≥ mx + b. It tells you that the y-intercept is c because the line hits the y-axis at (0,c). Hence the equation is now y ≥ mx + c. But now, we have to find the slope of the graph. This is found by "rise over run" (I am sure you have heard of this). Count how many units the graph went down/up and how many units the graph went left/right and put it in fraction form of (units down or up) / (units left or right). Well it moves 2 units down so plug -2 into the top. It moved 1 unit right, so plug +1 into the denominator. So, the slope is -2. Hence we finally have our formula: y ≥ -2x + c which is the 5th choice.
