This is a Area question.
In Primary school Area, we need to cut and paste.
Cut ABE and ADF. Paste together, you get half square area.
Triangle EFC is 1/8 of the square.
So 1/2 + 1/8 = 5/8 unshaded
1 – 5/8 = 3/8 shaded.
3/8 × 72 = 27 cm^2
Don’t try to use formula.
Primary school teacher only teach area of square, triangle, circle.