The area formula for rectangles is lxw. To solve, I would divide the figure up into 3 rectangles- top,middle and bottom, then find the areas and add them together.
Top: 4x13=52 cm^2
Middle: 5x8=40 cm^2
Bottom: 21x10=210 cm^2
(5 is the width of the middle piece. You get it from subtracting. 21-8-8=5. 13 is the width of the top piece. 5+8=13)
52+40+210
=302 cm^2
So your answer is 302 square centimetres.