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2014-02-12T00:31:15-02:00
Olá

 20 alunos--------100%
   7-------------------x

  20x=7.100%
  20x=700%
      x=700%/20
      x=35%
1 5 1
2014-02-12T00:35:26-02:00
Regra de 3 simples.

20 ----- 100%
7 -------   X

20x = 7.100
x = 700/20
x = 35%