How ?

[NoobHere]

 

[Dr.Peterson]

Because you didn't follow the guidelines here,

https://www.freemathhelp.com/forum/threads/guidelines-summary.112086/ ,​

I don't know what kind of help you need. So I'll just try to get you started.

Look at the two large triangles, whose intersection is the shaded area.

Can you find the area of each large triangle?

Then, if you added those two areas, how would the sum relate to the area of the entire figure?

 

[NoobHere]

I don't know where to start with. I found the height for the shaded area. But that doesn't help me. I think i need to find out the length of each side of the shaded triangle then i think should be able To solve. I tried but failed. Like no way to find.

 

[Dr.Peterson]

I don't know where to start with. I found the height for the shaded area. But that doesn't help me. I think i need to find out the length of each side of the shaded triangle then i think should be able To solve. I tried but failed. Like no way to find.

It turns out that the height of the shaded part isn't needed, but it's a good idea! In fact, none of the sides would help (or can be found), because nothing is known about their directions.

Look at the triangle whose apex is at upper left and whose base is horizontal. What is it's height? What is it's base? Can you find its area? Do so!

Then look back at my advice in post #2. I've given you the help you need.