Đáp án:
`e,` `3/4xx x-3/2=9/2`
`3/4xx x=9/2+3/2`
`3/4xx x=6`
`x=6:3/4`
`x=8`
`f,` `(3/20+1/2-x):32/9=21/128`
`3/20+1/2-x=21/128xx32/9`
`3/20+1/2-x=7/12`
`13/20-x=7/12`
`x=13/20-7/12`
`x=1/15`
`g,` `420:[75-(x-10)]=21`
`75-(x-10)=420:21`
`75-(x-10)=20`
`x-10=75-20`
`x-10=55`
`x=55+10`
`x=65`
`h,` `[25-(x+1,85)]:3=7`
`25-(x+1,85)=7xx3`
`25-(x+1,85)=21`
`x+1,85=25-21`
`x+1,85=4`
`x=4-1,85`
`x=2,15`
`i,` `x xx 2/3+1/5xx x=26,15`
`x xx(2/3+1/5)=26,15`
`x xx 13/15=26,15`
`x = 26,15:13/15`
`x=1569/52`
`k,` `3/4 xx x-1/4 xx x+2 xx x=3`
`x xx(3/4-1/4+2)=3`
`x xx 5/2=3`
`x=3:5/2`
`x=6/5`