(1).6(x/3+x-1/2 )=6(4x/3-1/2)=6×4x/3-6×1/2=8x-3
(2).(7-3a)+(5a-6)=7-3a+5a-6=2a+1
(3).(x-3)-(5x+7)=x-3-5x-7=-4x-10
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