Aregular square pyramid has a base length of 6 cm. the slant height of the pyramid is 9 cm. what is the surface area of the regular pyramid?
a 90 cm^2
b 120 cm^2
c 144 cm^2
d 252 cm^2

So..hmm check the picture below

the pyramid is really just 4 triangles and 1 square at the bottom, all stacked up to each other at the edges

get the area of the square bottom, is just a 6x6 square,  thus the name of the pyramid

and get the area of each triangle, notice the base  is 6, the altitude or height is 9

and add them all up, that's the surface area of the pyramid