algebra

A goldsmith has two gold alloys. The first alloy is 30% gold; the second alloy is 80% gold. How many grams of each should be mixed to produce 10 grams of an alloy that is 40% gold?
amount of 30% gold ___ g
amount of 80% gold ___ g

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  1. .3 a + .8 b = .4 * 10
    a + b = 10

    .3 a + .8 b = 4
    .8 a + .8 b = 8
    ---------------- subtract
    -.5 a = - 4

    a = 8
    so b = 2

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