May I please get help with other this problem for I am confused as I have tried multiple times to get the right answer

Using pythagoras
[tex]\begin{gathered} x^2=16^2+12^2 \\ x^2=256+144 \\ x^2=400 \\ \text{Take the square root} \\ x=20 \end{gathered}[/tex]The final answer
[tex]20[/tex]