To find the area of a parallelogram, you multiply the length and the width together, the exact same method you would use to find the area of a rectangle or square.
The reason you would use the same area formula of a rectangle/square to find the area of a parallelogram would be that all rectangles are parallelograms (however, not all parallelograms are rectangles). **Rectangles are a special kind of parallelogram: they are parallelograms with right angles formed in the corners of the figure.
Another thing to keep in mind is to imagine this: if you were to split the parallelogram from the top left corner straight down, you will get a triangular figure. If you were to move this triangular figure to fill in the right slanted part of the parallelogram, you would have a rectangle.
Now, to solve for the area. Because the formula is A=Base (or the length)*Height (or the width), you should have this expression: A=20*27
This would simplify to 540 cm squared, which would be your answer.