bài 1 a/-7/9+5/12-13/18=-28/36+15/36-26/36=(-28+15-26)/36=-39/36=-13/12
b/0,25.30.(2.1/3).8/45.0,5=1/4.30.7/3.8/45.1/2=14/9
c/ (4-5/12):4+5/24=(48/12-5/12):4+5/24
=43/12:4+5/24=43/48+5/24=43/48+10/48=53/48
bài 2 a/(9/2-2x):0,75=1 và 1/3
⇔(9-4x)/2. 4/3=4/3
⇔(9-4x)/2=1
⇔9-4x=2
⇔-4x=--7
→x=7/4
b/(-1/2x+2/3):-3/7=14/5
⇔-1/2x+2/3=14/5.(-3/7)=-6/5
⇔-1/2x=14/5-2/3=32/15
→x=-64/15
c/I-2/5x-1/5I-1/4=3/4
⇔ I-2/5x-1/5I=3/4+1/4=1
⇔-2/5x-1/5=1
⇔-2/5x=6/5
→x=-3