First your going to distribute the 3
3(-3x+15)
-9x+45
27=6x-9x+15
27=-3x+15
Then you’ll minus 15 from 27
27-15=12
12=3x
X=4
Pyramid Surface Area = (½ * Perimeter of Base * Slant Height) + Base Area
Base perimeter = 4 * 18 = 72 inches
Base Area = 18*18 = 324 square inches
Pyramid Surface Area = (.5 * 72 * 12) + 324
Pyramid Surface Area = 432 + 324
Pyramid Surface Area = 756 square inches
Source:
http://www.1728.org/volpyrmd.htm
She has a 50 percent chance she flips the coin on tails.