The equation of the plane containing the line y = 2 - x and the point (1, 0, 1) is
z = 2 - x - y, and this will be the equation of the upper boundary surface, (the top limit for z).
The bottom limit for z is the plane z = 0.
For the area in the xy plane, the upper boundary is the line y = 2 - x, and the lower boundary y = 0.
The limits on x are x = 1 and x = 2.