The answer is 30 ft²
The surface area (SA) of a pyramid is the sum of lateral area (LA) of the pyramid and the area of its base (BA):
SA = LA + BA
The area of the pyramid base (which is a square) with base edge a is:
BA = a²
We have:
SA = 55 ft²
LA = ?
a = 5 ft
LA = SA - BA = SA - a²
LA = 55 - 5²
LA = 55 - 25
LA = 30 ft²