Answer:
Area = 21/2 = 10.5 area units
Step-by-step explanation:
Two of the points are on the same line (the y-axis) as they both have x-coordinates of 0. This can thus be the base of your triangle.
Two more are on the same line (y= -9) as they both have the same y-coordinate of -9. This can be the height of your triangle.
So you have a base which is between -2 and -9 (7 units) and a height which is between 0 and 3 (3 units) so now just use the equation for area of a triangle