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2014-03-29T23:42:13-03:00
4(x+5)+3(x+5)=21
4x+20+3x+15=21
7x=21-20-15
x= -14/7
x= -2
4 3 4
2014-03-29T23:50:20-03:00
4(x+5) + 3(x+5) = 21
4x+20+3x+15=21
4x+3x=21-15-20
  7x= 21-35
  7x=-14
    x=-
 \frac{14}{7} =-2