In the given question the length and width of the plot are already given. although there is no direct specification regarding the one that is length or the one that is the width, so it can be taken as your own choice. This will not affect the ultimate answer.
So
Area of the rectangular plot = Length * Width
= 11.7 * 15.4 square cm
= 180.18 square cm
So the area of the rectangular plot as can be seen from the above deduction is 180.18 square centimeter.