1)111/37<x<91/13
\(\Leftrightarrow\)\(\frac{1443}{481}\)<x<\(\frac{3367}{481}\)
vậy x\(\in\)\(\left\{\frac{1444}{481};......;\frac{3366}{481}\right\}\)
2)-84/14<x<108/9
\(\Leftrightarrow\)\(\frac{-801}{126}\)<x<\(\frac{432}{126}\)
vậy x\(\in\)\(\left\{\frac{-800}{126};.......;\frac{431}{126}\right\}\)
3)\(\frac{-x}{4}\)=\(\frac{-9}{x}\)\(\Rightarrow\)-x.x=(-x)2=4.(-9)=-36
\(\Rightarrow\)(-x)2=-36=(-6)2
vậy -x=6;x=6