The idea is you graph the line y = (1/2)x-4, which is the same as y = 0.5x-4
This line goes through (0,-4) and (8,0) as the y and x intercepts. Make this line a solid line (due to the "or equal to" portion of the inequality sign). Then shade below this solid line to show the region of points that have smaller y coordinates compared to y = (1/2)x-4