Let's take a look at our triangle:
(drawing not to scale)
Using the Pythagorean Theorem, we would have that:
[tex]80^2+x^2=120^2[/tex]
Solving for x :
[tex]\begin{gathered} 80^2+x^2=120^2 \\ \rightarrow x^2=120^2-80^2 \\ \rightarrow x^{}=\sqrt[]{120^2-80^2} \\ \Rightarrow x=89.4\operatorname{cm} \end{gathered}[/tex]
We get that the other leg is 89.4 cm
