Answer:
335 mm²
Explanation:
This will be so easy, that you can do it in the future by yourself!
Okay let's start by splitting this figure, the easiest way seems to be by cutting off that little part, you know what just let me show a picture.
Okay you shuold be able to see the picture, so the small square has an area of 20, since 5 times 4 is 20 mm! The larger square has an area of 315!
How did I find this? Take that small 10mm in the side and add it to 5mm, that would be 15. 15 times the bottom the width, it would be 15 * 21. 15 times 21 is equal to 315.
Now, we add both those areas together, to get ourselves a nice little 335 mm²
I hope that helped, have a great day!!