Ta có x,y,z tỉ lệ với 5,4,3
=> \(\frac{x}{5}\)=\(\frac{y}{4}\)=\(\frac{z}{3}\)
=> x=5.k , y=4.k , z=3.k
=> y =\(\frac{x+2y-3z}{x-2y+3z}\)= \(\frac{5k+2.\left(4k\right)-3.\left(3k\right)}{5k-2.\left(4k\right)+3.\left(3k\right)}\)= \(\frac{5k+8k-9k}{5k-8k+9k}\)= \(\frac{4k}{6k}\)= \(\frac{2}{3}\)
vậy y = \(\frac{2}{3}\)