Find the area of the whole rectangle and find the area of the not shaded part and then subtract them to find the are of the shaded part.
Area of whole: 10 * 6 = 60 cm²
Area of non shaded: 6 * 2 = 12 cm²
Area of shaded part:
60 - 12 = 48 cm²
Hope this helps :)
I think H=P*2/4.2 could work corrext me if im wrong please
Here’s a photo on how to do it! If you need help in more problems like this use a website called Symbolab!! It’s really helpful!!