Đáp án + Giải thích các bước giải:
a)
`(2,5+x):1 4/7 =1 3/11`
`=>(5/2+x):11/7 =14/11`
`=>5/2+x=14/11. 11/7`
`=>5/2+x=2`
`=>x=2-5/2`
`=>x=4/2-5/2`
`=>x=(-1)/2`
b)
`|x+50%|+1 7/12 =7/12`
`=>|x+1/2|+19/12 =7/12`
`=>|x+1/2| =7/12-19/12`
`=>|x+1/2| =-1`
`=>` \(\left[ \begin{array}{l}x+\frac{1}{2}=1\\x+\frac{1}{2}=-1\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=1-\frac{1}{2}\\x=-1-\frac{1}{2}\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=\frac{2}{2}-\frac{1}{2}\\x=\frac{-2}{2}-\frac{1}{2}\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=\frac{1}{2}\\x=\frac{-3}{2}\end{array} \right.\)
Vậy `x∈{1/2;(-3)/2}`
c)
`(-1)/7 < x/21<1/3`
`=>(-3)/12<x/21<7/21`
`=>-3<x<7`
`=>x∈{-2;-1;0;1;2;3;4;5;6}`
Vậy `x∈{-2;-1;0;1;2;3;4;5;6}`
