Answer:
A. 20 square units
Explanation:
You want the area of the triangle whose vertices are A(2, 5), B(6, 1) and C(-4, 1).
Triangle area
The area of a triangle is given by the formula ...
A = 1/2bh
This triangle has a base of 10 units and a height of 4 units, so its area is ...
A = 1/2(10)(4) = 20 . . . . square units
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Additional comment
The length of the base is the difference of the x-coordinates of the points on the line y=1. The height is the difference in y-coordinates between point A and that line. You can do the arithmetic, or you can count the grid squares.