Answer:
12 square units
Step-by-step explanation:
You want the area of polygon FGHJ from its vertices, using some unspecified formula.
Formula
We don't know what formula you were given, but one that we like is ...
[tex]\displaystyle A=\dfrac{1}{2}\left|\sum_{k=1}^n{x_k(y_{k+1}-y_{k-1})}\right|[/tex]
This formula is implemented in the attached spreadsheet. The line marked Area gives half the absolute value of the sum of the numbers above.
Application
For the given points, the formula is computed by the attached spreadsheet. We recommend this approach whenever repetitive math is involved. You will note that repeating the first two point coordinates makes the formula more straightforward.
The area of this 4×3 rectangle is 12 square units.
