Question 209137
Let  a =  wt  of  25%,,,and  b=wt  of  10 %
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a+b=20#,,,,,b=20-a
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.25a +.1b =  .19*20 = 3.8,,,,,subst
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.25a +.1(20-a) =3.8
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.25a +2 -.1a = 3.8
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.15a = 1.8
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a=1.8/.15 = 12,,,,,b=20-12=8
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check,,,.25(12) +.1(8) = 3.8,,,,,,3+.8=3.8,,,,,ok
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