Answer:
x=16 cm
Step-by-step explanation:
By Pythagorean theorem:- [tex]a^2+b^2=c^2[/tex]
[tex]20^2=12^2+x^2[/tex]
[tex]x^2=400-144[/tex]
[tex]x^2=256[/tex]
[tex]x=16\:cm[/tex]
~
Hope this helps!
Check the picture below.