A triangle is always half the area of a rectangle for which it shares a side and has a third vertex on the opposite side of the rectangle.
So ADB is half the area of the square, and so is what's leftover, ADE+BDC. Since those are congruent because it's a midpoint, etc., each is one quarter the area of the square or one half the area of the middle triangle ADB.
Choice G. 1:2