Percentage problem

[puff2978]

Beaker A contains 3 liters of which 10%
is protein and the rest is fat. Beaker B contains 2 liters
of which an unknown percentage is protein and the rest
is fat. When the liquids are combined the result contain
x% protein and the rest is fat. What is the percentage
of protein in beaker B ?

 

[Denis]

Beaker  Total    Protein       Fat
   A      3        .3          2.7
   B      2         b          2-b
===================================
  A+B     5         x          5-x

x = .3 + b
5 - x = 4.7 - b

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