The system of equations is the equations of the two line
The flat line is constant (doesn't increase or decrease) and has a y-intercept at two, so the equation for it is y = 2. Notice the shaded region is above the line, and it is not a dotted line so it is y >= 2.
The second line has a y-intercept at 0 and seems to have a slope of 1, so the equation for it is y = x. Notice the shaded region is below the line, and it is a dotted line so it is y < x.
