math
posted by timmy .
The roof of a building is shaped like a square pyramid, with a base of 18m by 18m. If the slant height of the roof is 12m and roofing costs 5.75m2, how much will it cost for roofing material?

The lateral surface area of a pyramid (the slanted sides) is the perimeter of the base P multiplied by the slant height H and divided by two, or
A(lateral) = PH/2
Finally multiply by the price per metre^2 to get the price. 
so theres 4 sides to a pyramid does that mean each side is 18m?

Exactly!
The perimeter of the square base is therefore 4*18.
Useful information:
"18m x18m " is a short form for "each side of a square is 18m"