First find the area of the triangle: base multiply by heigh divided by 2:
B•H/2
= 12•12/2
=72m^2
Now find he area of the rectangle: base multiplied by height
B•H
= 9•3
= 27m^2
Lastly subtract the area of the rectangle to find the area of the shaded parts of the triangle.
= 72-27
= 45m^2
Therefore the area of the shaded part of the triangle is 45 meters squared.