Let b and h represent the length of the side of the base and the slant height, respectively. Then the total surface area is A = b² + 4*(1/2)bh A = b² +2bh
Substituting the given numbers, you have 336 = 12² +2·12·h 192 = 24h . . . . . . . . . subtract 12² = 144 8 = h . . . . . . . . . . . . . divide by 24