Answer: Choice C) 10.5
The distance from A to C is 7 units (count out the spaces between the two points, or subtract y coordinates 4-(-3) = 4+3 = 7)
Let AC = 7 be the base of the triangle. You might want to rotate the image so that AC is laying horizontally rather than being vertical.
Now move to point P. Walk 3 spaces to the right until you land on segment AC. This shows that the height of the triangle is 3 when the base is AC = 7.
base = 7, height = 3
area of triangle = (1/2)*base*height
area of triangle = 0.5*7*3
area of triangle = 10.5 square units
The shaded area is 299.59un^2.
This result is actually true for any exterior angle. The exterior angle of a triangle is equal to the sum of the two remote angles, and above is a short proof of it.
