Answer:
300 centimeters squared.
Explanation:
Given that a parallelogram has a base of 20 centimeters, a height of 15 centimeters, and a side length 21 centimeters, to determine the value of its area, the following calculation must be performed:
Area = Base x Height
Area = 20 x 15
Area = 300
Thus, the area of the parallelogram is 300 square centimeters.