Find the area of a polygon with the vertices of (–1, 5), (2, 5), (3, –1), and (–1, –1) a. 4 units2 b. 42 units2 c. 21 units2 d. 84 units2

To solve this problem you must apply the proccedure shown below:
 1. You have the following points given in the problem above:
  (–1, 5), (2, 5), (3, –1), and (–1, –1)
 2. When you plot each point on a graph, you can see that the figure is a trapezoid, therefore, the area of a trapezoid is:
 A=(B+b)h/2
 Where B is the larger base, b is the smaller base and h is the height.
 3. Base on the information, you have:
 B=4 units
 b=3 units
 h=6 units
 4. The area is:
 A=21 units²
 The answer is the option C: 21 units²