Let's first get this into a normal equation "y = mx + b" form.
-3x + 3y >= 12
3y >= 3x + 12
y >= x + 4
From this, we can find the x and y intercepts to make it easier to graph. After plugging in 0 for x and y, we get the two intercepts....
x - intercept: (0, -4)
y - intercept: (4, 0)
Then, since it is >= and not just >, the line is not dotted, but it is instead shaded in because those are included in the set of values for which y >= x + 4 is valid. Also, since it is >=, you shade above the line. From all of these, I can conclude it is Graph #4.