Since this is a 45-45-90 right triangle, the legs and hypotenuse have the relationship of: x, x, xsqrt(2) with x and x being the lengths of the legs and xsqrt(2) being the length of the hypotenuse.
As the hypotenuse measures 18 cm we would set xsqrt(2) equal to 18 and solve for x
xsqrt(2) = 18
x = 18 / sqrt(2)
x is approximately 12.73
which is not one of your answer choices, so I am assuming that either the question is not correct (my guess is the hypotenuse is actually 18sqrt(2) ), or the answer choices are not correct.
One way or the other, something is messed up here.
If the hypotenuse is in fact 18sqrt(2), then the legs will each be 18 in length.
Double check and get back to me if needed....
