Question 326228
The needed formula to find the altitude is 
A = (L)^2 + L(sqrt[(L)^2 + (2h)^2] 
A = surface area 
L = length of one side of the base 
h = height or altitude 
240 = (12)^2 + 12(sqrt[(12)^2 + (2h^2)] 
Can you take it from here and solve for h? 
http://en.wikipedia.org/wiki/Square_pyramid