We have to calculate the value of x.
We can relate the lengths of the sides of this right rectangle using the Pythagorean theorem:
[tex]\begin{gathered} x^2+12^2=13^2 \\ x^2=13^2-12^2 \\ x^2=169-144 \\ x^2=25 \\ x=\sqrt[]{25} \\ x=5 \end{gathered}[/tex]
Answer: x = 5
