A. what is the area of this polygon
B. Describes the steps taken to get this area

A. The area is 4 square units

B. The description is below

Break the figure into two parts along the dashed line. So we get a triangle on the left and a rectangle on the right.

The triangle has horizontal base of 3-1 = 2, and height 2. It's area is base*height/2 = 2*2/2 = 4/2 = 2 square units.

The rectangle is 1 by 2, so it's area is length*width = 1*2 = 2 square units.

Combine the two smaller areas to get the overall area: 2+2 = 4 square units

As an alternative, you can use the trapezoid area formula

b1 = 3 and b2 = 1 are the two parallel bases

h = 2 is the height

A = area of trapezoid

A = h*(b1+b2)/2

A = 2*(3+1)/2

A = 2*4/2

A = 8/2

A = 4 square units