[tex]{ \sf{ \red{using \: pythagoras \: theorem}}} \\ \\ { \sf {(20)}^{2} - {(16)}^{2} = {x}^{2} } \\ \\ { \sf{400 - 256 = {x}^{2} }} \\ \\ { \sf{144 = {x}^{2} }}[/tex]
[tex]{ \sf{x = \sqrt{144} }} \\ \\ { \boxed{ \boxed{ \green{x = 12}}}}[/tex]
option (C)
