Question 406737
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Hi
Let x represent the lbs of 15% aluminum
Question states***
  'Mixing' to form (500+x)lbx of 20%
 .15x + .22*500 = .20(500+x)
Solving for x
   .02*500= .05x
    .02*500/.05= x =200lb, the amount of 15% aluminum

CHECKING our Answer***
  30 + 110 = .20*700 = 140