Ta có: $\dfrac{x}{5}$ = $\dfrac{y}{4}$
⇒ $\dfrac{2x}{10}$ = $\dfrac{y}{4}$
`\text{Áp dụng dãy tỉ số bằng nhau, ta có: }`
$\dfrac{2x}{10}$ = $\dfrac{y}{4}$ = $\dfrac{2x + y}{10 + 4}$ = $\dfrac{28}{14}$ `= 2`
⇒ $\left \{ {{\dfrac{x}{5}=2} \atop {\dfrac{y}{4}=2}} \right.$
⇔ $\left \{ {{x=10} \atop {y=8}} \right.$
Vậy `x = 10; y = 8`