The area of a trapezium with the given dimensions is: 198 cm²
Area of a trapezium = 1/2(a + b)h, where h is the heght of the trapezium and a and b are the length of its bases.
Given the following:
Area of a trapezium = 1/2(12 + 21)12
Area of a trapezium = 198 cm²
Learn more about the area of trapezium on:
https://brainly.com/question/1463152