$a)\alpha ={50}^o$

$\beta ={70}^o$

$\gamma ={60}^o$

 

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

$\beta ={180}^o-{160}^o={20}^o$

$\gamma ={180}^o-{120}^o={60}^o$

 

$c)\alpha ={180}^o-{140}^o={40}^o$

$\beta ={70}^o$

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