If the base lengths are equal we know the base is a square. Therefore we use the formulas for area of a square for the base, and area of a triangle for the four sides.
Base = 12 * 12 = 144 sq cm
Sides = 4(1/2bh) = 4(1/2(12)(17)) = 4(6(17)) = 4(102) = 408 sq cm
144 + 408 = 552 sq cm
