The side of 6 is opposite a 30 degree angle in a 30 - 60 - 90 triangle
And the height of this triangle is opposite the 60 degree angle = √3 times 6 = 6√3
So.......the area of one of these triangles = (1/2) Base * Height =
(1/2) 6 * 6√3 = 18√3
But.....we have 4 of these equal triangles....so.....the area = 4 * 18√3 = 72√3