I have to find the length of x but I need guidance

Since we are dealing with a right triangle, we can use trigonometric identity below
[tex]\begin{gathered} sin\theta=\frac{O}{H} \\ \theta\rightarrow\text{ interior angle} \\ O\rightarrow\text{ opposite side to}\theta \\ H\rightarrow\text{ hypotenuse} \end{gathered}[/tex]Therefore, in our case,
[tex]\begin{gathered} sin(45\degree)=\frac{5}{x} \\ \Rightarrow x=\frac{5}{sin(45\degree)}=\frac{5}{\frac{1}{\sqrt{2}}}=5\sqrt{2} \end{gathered}[/tex]