The base of the pyramid is a square. We know that all sides of a square are equal so if we multiply the two sides of the base square(6*6) we get 36.
The area of a triangle can be found with the formula (b*h)/2. If we input the given values of 5 and 6 into our equation, then (5*6)/2 is 15 and since there are 4 triangles in the square pyramid, you multiply 15 by 4 (or add 15+15+15+15), and add the 36 from the base square.
