Volume of pyramid = 1/3*AH, where A is the area of the base and H is the height
Since we are given three sides of the triangle (the base of the pyramid), we should use Heron formula: Area of a triangle = sq.root of(s(s - a)(s - b)(s - c)), where s is the semi-perimeter (ie. the perimeter divided by 2) and a, b and c are side lengths. s = (5 + 12 + 13)/2 = 30/2 = 15 A = sq,root of(15(15 - 5)(15 - 12)(15 - 13)) = sq.root of (15*10*3*2) = sq.root of 900 = 30 m^2