First you have to draw an imaginary line to make two different shapes; a square and a triangle. Once you draw that line you find the area for the square and triangle.
Areas for square: A=l•h
A=8•9=72m
Now that you figured out the area for the square you find the area of the triangle
Area of triangle: A=1/2•b•h
To find the height you would subtract 12-8=4
A=1/2•9•4
A=18m
Now you add the two areas in order to figure out the whole space which is 18m+72m
So the area would be 90m
Hope this helped!