Mixture problem solving

Question

How much of an alloy that is 30% copper should be mixed with 600 ounces of an alloy that is 70% copper in order to get an alloy that is 50% copper?

Answer 1

.3x + .7(600) = .5(x+600)

.5x -.3x = 420-300

.2x = 120

x = 120/.2 = 600

.5-.3 = .2

.7-.5 = .2

equal amounts will be needed

600 of each