The volume of a pyramid is (area of base x height) / 3 In this case the base is an equilateral triangle with side 12cm. Using the semi perimeter formula gives Base = sr( 18 x 6 x 6 x 6) = 62.3538... Volume = 62.3538... x 14 / 3 = 290.9845... = 291 to nearest whole number
You could find the base area using Pythagoras and 1/2bh or the Sine formula