\(\frac{x}{3}=\frac{y}{3}\)=> \(\frac{x}{15}=\frac{y}{15}\)
\(\frac{y}{5}=\frac{z}{7}\)=> \(\frac{y}{15}=\frac{z}{21}\)
=> \(\frac{x}{15}=\frac{y}{15}=\frac{z}{21}\)
=> \(\frac{2x}{30}=\frac{3y}{45}=\frac{z}{21}=\frac{2x+3y-z}{30+45-21}=\frac{372}{54}=\frac{62}{9}\)
=> x = 62 . 15 : 9 = \(\frac{310}{3}\)
y = 62 . 15 : 9 = \(\frac{310}{3}\)
z = 62 . 21 : 9 \(\frac{434}{3}\)