Đáp án + Giải thích các bước giải:
Bài `3` :
`a)` `2/3x+1/4=7/12`
`=>2/3x=7/12-1/4`
`=>2/3x=7/12-3/12`
`=>2/3x=4/12=1/3`
`=>x=1/3:2/3`
`=>x=1/3*3/2=1/2`
Vậy `x = 1/2`
`b)` `3/4+1/4x=3 1/3`
`=>3/4+1/4x=10/3`
`=>1/4x=10/3-3/4`
`=>1/4x=40/12-9/12`
`=>1/4x=31/12`
`=>x=31/12:1/4`
`=>x=31/12*4=31/3`
Vậy `x = 31/3`
`c)` `9/4:(x - 7 1/3)=-1,5`
`=>9/4:(x-22/3)=-3/2`
`=>x-22/3=9/4:(-3/2)`
`=>x-22/3=9/4*(-2/3)`
`=>x-22/3=-3/2`
`=>x=-3/2+22/3`
`=>x=-9/6+44/6=35/6`
Vậy `x = 35/6`
`d)` `(3/4x-0,75):3/7=14/5`
`=>(3/4x-3/4)=14/5*3/7`
`=>3/4x-3/4=6/5`
`=>3/4x=6/5+3/4`
`=>3/4x=24/20+15/20`
`=>3/4x=39/20`
`=>x=39/20:3/4`
`=>x=39/20*4/3=13/5`
Vậy `x = 13/5`.
