a)
[tex]\beta =180^o-(2\alpha -10^o)-(\alpha +50^o)=180^o-2\alpha +10^o-\alpha -50^o=\\=180^o-3\alpha-40^o=\underline{140^o-3\alpha}\\[/tex]
b)
[tex]\beta=180^o-(65^o-3,5\alpha)-(0,5\alpha+25^o)=180^o-65^o+3,5\alpha-0,5\alpha-25^o=\\=180^o-90^o+3\alpha=\underline{90^o+3\alpha}[/tex]
