b) Có $\frac{x}{35}$= $\frac{y}{50}$->$\frac{x}{35}$=$\frac{y}{50}$
Áp dụng t/c dãy tỉ số = nhau
->$\frac{x}{35}$=$\frac{y}{50}$=$\frac{2x-y}{2.35-50}$= $\frac{-40}{20}$ = -2
-> $\frac{x}{35}$= -2 -> x=-70
$\frac{y}{50}$= -2 -> y= -100
Vậy ........
c) 5x= 8y-> $\frac{x}{8}$= $\frac{y}{5}$
Áp dụng t/c dãy tỉ số = nhau
-> $\frac{x}{8}$= $\frac{y}{5}$ = $\frac{y-x}{5-8}$ = $\frac{-12}{-3}$= 4
-> $\frac{x}{8}$= 4 -> x= 32
$\frac{y}{5}$=4 -> y= 20
Vậy..........
