Giải thích các bước giải:

a.Ta có:

$\dfrac{x}5=\dfrac{y}3=\dfrac{x+y}{5+3}=\dfrac{1.6}8=0.2$

$\to x=1,y=0.6$

b.Ta có:

$\dfrac{x}4=\dfrac{y}{-7}=\dfrac{3x}{12}=\dfrac{y}{-7}=\dfrac{3x+y}{12-7}=\dfrac{20}5=4$

$\to x=16, y=-28$

c.Ta có:

$x:y=2\dfrac23$

$\to \dfrac{x}y=\dfrac83$

$\to \dfrac{x}8=\dfrac{y}3=\dfrac{x-y}{8-3}=\dfrac{60}5=12$

$\to x=96, y=36$

d.Ta có:

$x:3=y:16\to \dfrac{x}3=\dfrac{y}{16}=\dfrac{3x}9=\dfrac{y}{16}=\dfrac{3x-y}{9-16}=\dfrac{35}{-7}=-5$

$\to x=-15, y=-80$