Question

na figura, sabendo que AB = AC = CD e que o ângulo D mede 20° determine a medida de x

Answer 1

$\large\boxed{\begin{array}{l}\rm x+100^\circ+20^\circ=180^\circ\\\rm x=180^\circ-100^\circ-20^\circ\\\rm x=60^\circ\end{array}}$