در کدام گزینه مقدار x آمده است؟
20 درجه
30 درجه
15 درجه
10 درجه
\(\begin{array}{l}AB = CD \Rightarrow \mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}} \over A} \mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}} \over B} = \mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}} \over C} \mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\frown$}} \over D} \Rightarrow 3x + 20^\circ = 80^\circ \\\\ \Rightarrow 3x = 80^\circ - 20^\circ = 60^\circ \Rightarrow x = 20^\circ \end{array}\)