$\def\arraystretch{1.25} \begin{aligned}2 \alpha + 2 \beta &= 360°\quad \quad |:2 \\\alpha + \beta &= 180° \end{aligned}$

Setze den gegebenen Wert für $\alpha$ ein.

$\def\arraystretch{1.25} \begin{aligned} 92°+ \beta &=180°\quad\quad|-92°\\\beta &=88°\end{aligned}$

$\def\arraystretch{1.25} \begin{aligned} \alpha + 2\alpha + 2\alpha + \alpha &=360° \\6\alpha &=360°\quad \quad |:6\\\alpha &=60°\end{aligned}$

$\def\arraystretch{1.25} \begin{aligned}\alpha+(\alpha + 20°)+ \alpha + (\alpha+20°) &= 360°\\4\alpha+40° &=360° \quad |-40°\\4\alpha &=320°\quad|:4\\\alpha &=80°\end{aligned}$