Graphing the inequalities
y ≥ 0 are the points above the x-axis including the points along the x-axis
y < x are the points below the line y = x
x + y < 6 are the points below the line x + y = 6
The solution to this is the region bounded by the lines connecting the points
(0, 0)
(0, 6)
(3, 3)