Hi!
I have attached 2 images that should help you understand :)
First, look at the edits I made to the image you posted. I separated the shape into smaller shapes so that we can find the area of each individual one.
Let's start with the rectangle.
To find the area of a rectangle, multiply the width times the height.
10 · 4 = 40
Rectangle = 40cm
Next up, the red triangles.
I have included another image showing the triangles combined into rectangles. So we can find the area of the triangles just like we would rectangles!
(let me know if you don't understand how I found the width + height of the triangles)
5 · 10 = 50
Red triangles = 50cm
And finally, the green triangles.
8 · 7 = 56
Green triangles = 56cm
Add it all together and you get...
40 + 50 + 56 = 146
The answer to the question is 146cm.
Next time you are having trouble with something like this, picture the triangles as rectangles! :)
