Explain how to do the basic math to determe 3.14 x diameter 2squared?

Your question doesn't make sense. The area of a circle is Pi (approximately 3.14) times the RADIUS squared. An example would be a circle with a diameter of 6 inches and thus the circle would have a radius of 3 inches. Three squared (3 times 3) is 9, and 9 times Pi is approximately 28.3 square inches.