`a,` `-x/7=6/y=-14/49`
`⇒-x/7=6/y=-2/7`
$⇒\begin{cases}\dfrac{-x}7=\dfrac{-2}{7}\\\\\dfrac6y=\dfrac{-2}{7}\end{cases}$
$⇒\begin{cases}x=\dfrac{-2}{7}.(-7)\\\\y=6:\dfrac{-2}{7}\end{cases}$
$⇒\begin{cases}x=\dfrac{-2.(-7)}{7}\\\\y=\dfrac{-7.6}{2}\end{cases}$
$⇒\begin{cases}x=2\\\\y=-21\end{cases}$
`b,` `-15/10=x/8=24/y`
`⇒-3/2=x/8=24/y`
$⇒\begin{cases}\dfrac{x}8=\dfrac{-3}2\\\\\dfrac{24}y=\dfrac{-3}2\end{cases}$
$⇒\begin{cases}x=\dfrac{-3}{2}.8\\\\y=24:\dfrac{-3}{2}\end{cases}$
$⇒\begin{cases}x=\dfrac{-3.8}{2}\\\\y=\dfrac{-2.24}{3}\end{cases}$
$⇒\begin{cases}x=-12\\\\y=-16\end{cases}$
