Finding the area of an irregular figure

[DepressedPepe]

View attachment 8052
If u know a equation for finding the area please submit it.
Or a way to do it without using a program such as "Geogebra".

Thanks in advance.

 

[Greg]

$5\cdot3=15\text{ sq. units}$.

 

[mrtwhs]

Any quadrilateral whose diagonals $$d_1$$ and $$d_2$$ are perpendicular will have area equal to $$\dfrac{1}{2}d_1d_2$$.