$a)\alpha ={180}^o-{135}^o={45}^o$    

`beta=52^o 

$\gamma ={180}^o-\left({45}^o+{52}^o\right)={180}^o-{97}^o={83}^o$  

 

$b)\alpha ={180}^o-{120}^o={60}^o$  

$\beta ={50}^o$  

$\gamma ={360}^o-\left({60}^o+{50}^o+{145}^o\right)={360}^o-{255}^o={105}^o$