Trình bày lời giải:
`e)`
`(-0,65)/(0,91)=(-6,55)/x`
`=>-0,65.x=-6,55.0,91`
`=>-0,65.x=-5,9605`
`=>x=-5,9605:(-0,65)`
`=>x=9,17`
Vậy `x=9,17`
`f)`
`x/(2,7)=(0,7)/(6,3)`
`=>x.6,3=2,7.0,7`
`=>x.6,3=1,89`
`=>x=1,89:6,3`
`=>x=0,3`
Vậy `x=0,3`
`g)`
`(2,4)/x=(5,4)/(13,5)`
`=>x.5,4=2,4.13,5`
`=>x.5,4=32,4`
`=>x=32,4:5,4`
`=>x=6`
Vậy `x=6`
`h)`
`1/2:x=3/4:21/4(xne0)`
`=>1/2:x=3/4 . 4/21`
`=>1/2:x=1/7`
`=>1/2 . 1/x=1/7`
`=>1/(2x)=1/7`
`=>2x=7`
`=>x=7:2`
`=>x=7/2`
Vậy `x=7/2`