15)
[tex]\displaystyle\bf\\3x=4y\\\\\frac{x}{y}=\frac{4}{3}\\\\\\\frac{x+2y}{x+5y}=~~(Simplificam~fortat~cu~y)\\\\\\=\frac{\dfrac{x}{y}+\dfrac{2y}{y}}{\dfrac{x}{y}+\dfrac{5y}{y}}=\frac{\dfrac{4}{3}+2}{\dfrac{4}{3}+5}=\frac{\dfrac{4+2\cdot3}{3}}{\dfrac{4+5\cdot3}{3}}=\frac{\dfrac{10}{3}}{\dfrac{19}{3}}=\boxed{\bf\frac{10}{19}}[/tex]
