Theory
A compound shape is made from two or more simpler shapes.
The safest method is to split the shape into rectangles, triangles or trapezia that you already know how to calculate.
Sometimes it is easier to find a large outer rectangle and subtract the missing piece.
Before finding area, calculate any missing lengths from the diagram. Opposite horizontal or vertical lengths often help.
Label each part clearly. Edexcel method marks often reward a correct split even if one arithmetic step is wrong.
For L-shapes, check whether your split creates two rectangles with no overlap. If they overlap, you may count part of the shape twice.
For cut-out shapes, find the area of the full outer rectangle first, then subtract the missing rectangle.
Write units at the end. Compound area still uses square units.