Rectangle abcd has vertices a(-3, 1), b(5, 7), c(9, 4), and d(1, -2). calculate the area of rectangle abcd.

It's not a rectangle. Look at the picture.

It is a parallelogram.

The area of the red rectangle:

The areas of the right triangles:

The area of a parallelogram:

you can first factor out the n to get n(1+5). we know that 1+5 is 6, so we just have 6n.