[tex]x=3[/tex]
1) Note that this is a right triangle, and we can tell an isosceles one by the marks on the triangle.
2) So, we can use the Pythagorean Theorem, to find the side lengths since all we know for now is the hypotenuse:
[tex]\begin{gathered} a^2=b^2+c^2 \\ (3\sqrt[]{2})^2=x^2+x^2 \\ 2x^2=9\cdot2 \\ 2x^2=18 \\ \frac{2x^2}{2}=\frac{18}{2} \\ x^2=9 \\ x=\sqrt{9},\: -\sqrt{9} \\ x=-3,3 \end{gathered}[/tex]
We can discard the negative value for there is no negative length. So, the answer is 3
