1.a)1/7.1/2+1/7.1/3-5/6.1/7=1/7.(1/2+1/3-5/6)=1/7.(3/6+2/6-5/6)=1/7.0=0
b)-1/2.3/5.8/9.-25/4=-1.3.2.4.5.(-5)/2.5.3.3.4=5/3
c)đề bài=16/5÷16/5+9/2.76/45÷-43/2=1+9/2.76/45.-2/43=1+(-76/215)=-76+215/215=139/215
2.a)đề bài⇒-3/2.2/15+x=4x-2
⇒-1/5+x=4x-2
⇒x-4x=-2+1/5
⇒-3x=-9/5
⇒x=-9/5:(-3)=3/5
b)đề bài ⇒x-1/2=0 hoặc 2x-2/3=0
TH1:x-1/2=0⇒x=0+1/2=1/2
TH2:2x-2/3=0⇒2x=2/3⇒x=2/3:2=1/3
Vậy x=1/2,x=1/3