3x+y<6, y<6-3x. Plot the line y=6-3x, which has y intercept at 6 (x=0) and x intercept at 3x=6, or x=2 (y=0). Draw a straight line through the intercepts (0,6) and (2,0). On the line y=6-3x. To the left of this line, which slopes backwards, y<6-3x. As well as the area of the triangle enclosed by the line and the two axes, y is less than 6-3x for the whole region to the left of the line for positive and negative values of x and y. So graphically, the line itself and the whole region to its left represents the inequality.