Previously, we were trying to find the area of the non-shaded region. You will probably have found that the upper line must be parallel to the horizontal sides, and situated 2/3 of the way up the vertical ones. We know this because the steep diagonal lines clearly end 4/3 of the way across the top. This makes the slope of the steep diagonal line 1.5. The shallow diagonals must have slopes of 2/3. It follows that the lower intersections are 1/6 of the way through. This makes the lower shaded triangles both have area (1/3 * 1/2 / 2) – (1/3 * 1/6) = 1/18 each (A=B*H/2.) The upper shaded triangle clearly has base 1/2; and, height 1/3 as we showed earlier. This makes it’s area 1/12. This means the total shaded area 1/18 + 1/18 + 1/12 = 7/36, and the non-shaded, 1 – 7/36 = 29/36. The answer is therefore 29/36.