The method used would be Factoring, and the answers are x = 1 and x = 12.
Since there is an x^2 and you'd have to solve for each x, you would have to factor.
To do this, you'd find 2 factors of 12 that when multiplied equal 12, but when added equal -13.
-1*-12 = 12
-1 + -12 = -13
Meaning the factors are -1 and -12.
Next you factor down the x^2 to make it say "x, add or subtract factor based on sign (plus or minus) equals 0. They would look like this...
X - 1 = 0
X - 12 = 0
Solve for the x's.
Thus making the answers for "x" 1 and 12.
I hope this helps!