Triangle QRS with vertices Q(6, -2), R(4, -7), and S(2, -5), is drawn inside a rectangle, as shown below. What is the area, in square units, of the triangle QRS?A- 7B-10C-13D-18

The rectangle is 4 x 5. Area of 20. 
The three triangles that are cut off from the rectangle to make QRS have areas of 5, 2, and 6. 13 total cut off. 
Subtract 13 from 20. 
20 - 13 = 7. 
The answer is A, 7. Hope this helps!