A jeweler wants to make a silver alloy to be used to make necklaces. How many ounces of a silver alloy that costs $3.50 per ounce should be mixed with one that costs $7.00 per ounce to make a new 30-ounce alloy that costs $6.30 per ounce

Answer 1

X oz. @ $3.50/oz.
(30-X) oz. @ $7.00/oz.

3.50x + 7.00(30-x) = 6.30*30
3.5x + 210 - 7x = 189
-3.5x = 189 - 210 = -21
X = 6 oz. @ 3.50/oz.
30-X = 30-6 = 24 oz. @ $7.00/oz.