3x-[1-(2+3x)]=7
3x-1+2+3x=7
3x+3x=7-2+1
6x=6
x=6÷6
x=1
1/2(x+2)=1-1/3(x-5)
两边乘6
3x+3=6-2x+10
3x+2x=6+10-3
5x=13
x=13÷5
x=13/5
1/2(x-3)=2-1/2(x-3)
1/2(x-3)+1/2(x-3)=2
x-3=2
x=3+2
x=5