[tex]\dfrac{7x+5y}{5x+3y}=\dfrac{87}{17}[/tex]
[tex]\dfrac{x}{y}=\dfrac{8}{5}[/tex]
[tex]\dfrac{x}{y}=\dfrac{8}{5} => x=8a ; y=5a[/tex]
[tex]\dfrac{7x+5y}{4x-3y}=\dfrac{87}{17}[/tex]
[tex]\dfrac{7\cdot8a+5\cdot5a}{4\cdot8a-3\cdot5a}=\dfrac{87}{17}[/tex]
[tex]\dfrac{56a+25a}{32a+15a}=\dfrac{87}{17}[/tex]
[tex]87(32a+15a)=17(56a+25a)[/tex]
[tex]2784a+1305a=952a+425a[/tex]
[tex]4089a=1377a[/tex]
