a)
[tex] {180}^{o} = {60}^{o} + 2 \alpha + \alpha \\ {180}^{o} = {60}^{o} + 3 \alpha \\ {120}^{o} = 3 \alpha | \div 3 \\ \alpha = {40}^{o} [/tex]
Zatem
[tex]2 \alpha = {60}^{o} \times 2 = {120}^{o} [/tex]
b)
[tex]10 = a + 4a - 5 \\ 10 = 5a - 5 \\ 5a = 15 | \div 5 \\ a = 3[/tex]
Zatem
[tex]4a - 5 = 4 \times 3 - 5 = 12 - 5 = 7[/tex]
