$a)$

$\beta ={100}^o$

$\alpha ={180}^o-{100}^o={80}^o$

 

 

$b)$

$\alpha ={45}^o$

$\beta ={180}^o-\left({45}^o+{60}^o\right)={180}^o-{105}^o={75}^o$

$\gamma ={180}^o-{45}^o={135}^o$

$\delta ={60}^o+\alpha ={60}^o+{45}^o={105}^o$

 

 

$c)$

$\delta ={180}^o-{50}^o={130}^o$

$\alpha ={180}^o-\left({70}^o+{50}^o\right)={180}^o-{120}^o={60}^o$

$\beta ={70}^o$

$\gamma ={180}^o-{70}^o={110}^o$