How many ounces of an alloy containing 30% gold on the world market must be added to 10 ounces of an alloy containing 5% to produce an alloy containing 20% gold?

Answer 1

amount of the 30% alloy to be added --- x ounces

.3x + .05(10) = .2(10+x)
.3x + .5 = 2 + .2x
.1x = 1.5
x = 15