The Pythagorean Theorem states that the hypotenuse of a right triangle is equal to the square root of the sum of its squared sides, mathematically:
h^2=x^2+y^2, where h=hypotenuse and x and y are the side lengths.
In this case we can say:
(√117)^2=6^2+x^2
117=36+x^2
x^2=117-36
x^2=81
x=√81 since x>0
x=9 cm