We are given a right-angled triangle.
Recall that the Pythagorean theorem is given by
[tex]a^2+b^2=c^2[/tex]
Where a and b are the shorter sides and c is the longest side.
For the given case, one shorter side (12) and the longest side (13) is given
Let us find the other shorter side (x)
[tex]\begin{gathered} a^2+b^2=c^2 \\ a^2=c^2-b^2 \\ a^2=13^2-12^2 \\ a^2=169-144 \\ a^2=25 \\ a=\sqrt[]{25} \\ a=5 \end{gathered}[/tex]
Therefore, the third side x is 5
[tex]x=5[/tex]
