$\text{a)}$

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

$\alpha =180-\angle \text{BCA}-\angle \text{CBA}=180-\left(180-110\right)-\left(180-130\right)=180-70-50={60}^o$

 

$\text{b)}$

$\beta =180-\left(180-90-40\right)=180-130={50}^o$

$\gamma =180-2\cdot 40=180-80={100}^o$

$\alpha =180-90-40={50}^o$

 

$\text{c)}$

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

$\alpha =90-\gamma =90-60={30}^o$

$\beta =180-\alpha =180-30={150}^o$

 

$\text{d)}$

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

$\beta =180-90-\alpha =180-90-40={50}^o$

$\gamma =180-2\cdot \beta =180-100={80}^o$