Apyramid has a square base with sides 8" and a slant height of 5". total area =

Check the picture below.

so, as you can see, the bottom of it is just a 8x8 square, whilst one of the 4 triangular faces is just a triangle with a base of 8 and a height of 5.

so, we can simply get the area of the base and the 4 triangular faces and sum them up, that's the surface area of the pyramid.