There is no equation here because of the lack of an equal sign. Thus, there cannot be any "solving."
I took the liberty to add the "=" sign !!!
Solve for x:
x^2 - 18 x - 77 = 0
Add 77 to both sides:
x^2 - 18 x = 77
Add 81 to both sides:
x^2 - 18 x + 81 = 158
Write the left hand side as a square:
(x - 9)^2 = 158
Take the square root of both sides:
x - 9 = sqrt(158) or x - 9 = -sqrt(158)
Add 9 to both sides:
x = 9 + sqrt(158) or x = 9 - sqrt(158)