[tex] x^2 + (x + 3)^2 = (\sqrt{117})^2 [/tex]
[tex] x^2 + x^2 + 6x + 9 = 117 [/tex]
[tex] 2x^2 + 6x -108 = 0 [/tex]
[tex] x^2 + 3x - 54 = 0 [/tex]
[tex] (x + 9)(x - 6) = 0 [/tex]
[tex] x + 9 = 0 ~~or~~ x - 6 = 0 [/tex]
[tex] x = -9 ~~ or~~ x = 6 [/tex]
Since the side of a triangle cannot have a negative length, we discard the solution x = -9.
Answer: x = 6