Hello!
This shape is a "Strange" shape, but if you look closer at it, you can see that it can be divided into "normal shapes" like rectangles and squares
On the bottom on the "polygon" we can dived it into 2 squares
One square would have the dimensions of 6 and 6
The other one would have 4 and 6
The formula of area is: Base*Height
So the first square would have an area of 36
The second square would have an area of 24
Now we solve for the big rectangle
On first thought, it may seem like the dimensions are 16 and 25, but it is actually 10 and 25. Because 16 is the whole height of the polygon.
So we subtract it by 6
So the big rectangle is 250
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Now we add the areas together to get a total result of 310
If you have questions, feel free to ask