Question 362094
First system : x+y<8 and 
Second System : x<=4 if you want to solve these systems separately. 

First think that x+y = 8 and plot this such that;
*[invoke describe_linear_equation 1, 1, 8 ]
 
After then you will see that the original equation is x + y < 8 so that you have to modify your line like a discontinuous line(not ____ like _ _ _) and rake the below part of the line because you want the smaller values rather than 8. I hope I could explain it in here because I can not draw it..

The second system is also in same logic.. think like x =4 and plot it
After then you will see that the original equation is x<= 4 so that at this time you do not have to modify your line because it includes 4 and rake the left part of the line because you want the smaller and equal values rather than 4.

RF.