Giải thích các bước giải:
a.Ta có:
$3x=2y\to 3x+3y=5y$
$\to 3(x+y)=5y$
$\to 3\cdot 10=5y$
$\to 5y=30$
$\to y=6$
$\to 3x=12\to x=4$
b.Ta có:
$\dfrac{x-2}{y+3}=\dfrac46=\dfrac23$
$\to 3(x-2)=2(y+3)$
$\to 3x-6=2y+6$
$\to 3x-2y=12$
$\to x+(2x-2y)=12$
$\to x+2(x-y)=12$
$\to x+2\cdot 4=12$ vì $y-x=-4\to -(y-x)=4\to x-y=4$
$\to x+8=12$
$\to x=4\to y=x-4=0$ vì $y-x=-4$
c.Ta có:
$\dfrac{x}{4}=\dfrac{y}{-10}=\dfrac{2y}{-20}=\dfrac{x+2y}{4-20}=\dfrac{12}{-16}=-\dfrac34$
$\to x=-3, y=\dfrac{15}{2}$
