the assumption here, being that it's a square pyramid, thus its base is a square, namely a 6x6, Check the picture below.
notice, the pyramid has four triangular faces with a height of 9 and a base of 6, and the squarish base, so we can simply get the area of each of those figures and sum them up.
[tex]\bf \stackrel{\textit{area of four triangles}}{4\left[\cfrac{1}{2}(6)(9) \right]}+\stackrel{\textit{area of base}}{(6\cdot 6)}\implies 108+36\implies 144[/tex]
