Consider the 3 x 3 square below
The whole area = 3 * 3 = 9
The area of triangle MPC = (1/2) (1.5) (1) = .75
The area of triangle BPC = (1/2) (3)(1) = 3/2 = 1.5
Area of triangle APB = (1/2) (3) (2) = 3
So the area of the remaining quadrilateral = is 9 - .75 - 1.5 - 3 = 3.75
The only question I have is the ratios of what ???.....of each area to the whole area ???
If so
MPC / 9 = .75/9 = 1/12
BPC / 9 = 1.5/9 = 2/12 = 1/6
APB / 9 = 3/9 = 4/12 = 1/4
And APMD / 9 = 3.75/9 = 5/12