If you add right triangles to each side, you can create a rectangle and then subtract the right triangles. So extending the sides makes the new coordinates (0,1), (3,1), (3,5), (0,5). Now the area is simple to find for this rectangle, it is simply 4*3=12. If you combine the 2 triangles, you make half of the rectangle, or a square in this case. So taking half of 12 gets 6, which is the area. b. 6 units
