a) 

$\beta$ $={75}^o$

$\alpha$ + $\beta$ $+{75}^o={180}^o$

$\alpha$ $={180}^o-{75}^o-{75}^o={30}^o$

b)

$\alpha =\beta$

$2\alpha ={180}^o-{130}^o$

$2\alpha ={50}^o$

$\alpha ={25}^o$

$\beta ={25}^o$

c)

$\alpha =\beta$

$2\alpha ={180}^o-{60}^o$

$2\alpha ={120}^o$

$\alpha ={60}^o$

$\beta ={60}^o$

Trójkąt równoboczny

d)

$\alpha =\beta$

$2\alpha ={180}^o-{90}^o$

$2\alpha ={90}^o$

$\alpha ={45}^o$

$\beta ={45}^o$