$\text{$\dfrac{x}{3}$=$\dfrac{y}{5}$=$\dfrac{z}{7}$}$
$\text{$\Rightarrow$ $\dfrac{2x}{6}$=$\dfrac{y}{5}$=$\dfrac{3z}{21}$}$
$\text{$\Rightarrow$ $\dfrac{2x-y+3z}{6-5+21}$}$
$\text{$\Rightarrow$ $\dfrac{110}{22}$=5}$
$\text{+$\dfrac{x}{3}$=5 $\Rightarrow$ x=15}$
$\text{+$\dfrac{y}{5}$=5 $\Rightarrow$ y=25}$
$\text{+$\dfrac{z}{7}$=5 $\Rightarrow$ x=35}$
