Odpowiedź:
[tex]a) \: \: z = 5 \times x + 15 \times y = 5 \times \frac{12}{10} + 15 \times \frac{1}{5} = 6 + 3 = 9[/tex]
[tex]b) \: \: z = \frac{2}{3} \times x - 1.5 \times y = \frac{2}{3} \times \frac{12}{10} - \frac{3}{2} \times \frac{1}{5} = \frac{4}{5} - \frac{3}{10} = \frac{5}{10} = \frac{1}{2} [/tex]
[tex]c ) \: \: z = \frac{x + y}{x - y} = \frac{ \frac{12}{10} + \frac{1}{5} }{ \frac{12}{10} - \frac{1}{5} } = \frac{ \frac{7}{5} }{ \frac{4}{5} } = \frac{7}{5} \times \frac{5}{4} = \frac{7}{4} = 1 \frac{3}{4} [/tex]
