Pyramid Surface Area = (½ * Perimeter of Base * Slant Height) + Base Area
2(x-5)=20
Divide both sides by 2 (division of property equality)
x - 5 = 10
Add 5 to both sides (addition of property equality)
x = 15
Answer
x = 15 is the solution
Number 15 is 80 i dont know about the others...sorry