Respuesta :
[tex]\bf \textit{using the pythagorean theorem} \\\\ c^2=a^2+b^2\implies c=\sqrt{a^2+b^2} \qquad \begin{cases} c=\stackrel{hypotenuse}{x}\\ a=\stackrel{adjacent}{20}\\ b=\stackrel{opposite}{21}\\ \end{cases} \\\\\\ x=\sqrt{20^2+21^2}\implies x=\sqrt{841}\implies x=29[/tex]