Salut! :)
Răspuns:
[tex]\dfrac{61}{55}[/tex]
Explicație pas cu pas:
[tex]0,7 = \frac{7}{10}[/tex]
[tex]\dfrac{x}{y} = \dfrac{7}{10} \Longrightarrow y = \dfrac{10x}{7}[/tex]
[tex]\dfrac{3x + 4y}{5x + 2y} = \dfrac{3x + 4 \cdot \frac{10x}{7} }{5x + 2\cdot\frac{10x}{7} } =[/tex]
[tex]= \dfrac{3x +\frac{40x}{7} }{5x + \frac{20x}{7} } =[/tex]
[tex]= \dfrac{\dfrac{61}{7} x}{\dfrac{55}{7} x} =[/tex]
[tex]= \dfrac{61}{55}[/tex]
