2.
[tex] \frac{10}{x} = \frac{y}{5} = > x \times y = 5 \times 10 = 50[/tex]
[tex]3xy - 1 = 3 \times 50 - 1 = 150 - 1 = 149[/tex]
3.
[tex]tg \: b = \frac{ac}{ab} = \frac{3}{4} [/tex]
[tex]\it tgB=\dfrac{AC}{AB}=\dfrac{3}{4}=0,75[/tex]
