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2013-09-02T19:18:06-03:00
A) 3x+5=10   
3x=10-5
3x=5
x=5/3

B)x-(2x-1)=20
x-2x+1=20
x-2x=20-1
-x=19 (-1)
x=-19

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2013-09-02T19:23:45-03:00
C)
2x-(x-1)=9-(x-3)
2x-x+1=9-x+3
2x=11
x=11/2

D)
3(2x+7)+3(3x-5)=3(4x+5)-1
6x+21+9x-15=12x+15-1
6x+9x-12x=15-1+15-21
3x=8
x=8/3