Ametalworker has a metal alloy that is 20% copper and another alloy that is 60% copper. how many kilograms of each alloy should the metalworker combine to create 120 kg of a 44% copper alloy?

Let x=the mass of 20% copper Let y=the mass of 60% copper x+y=80kg .20x+.60y=.52(80)% .20x+.60y=41.6% Substitute or use elimination to find the amounts needed of 20% copper alloy and the amount of 60% copper alloy to make 80kg of 52% copper alloy
break it down- 
It's .52(80)%, so 52% of 80 kg
If you're stuck you can try to find y by subtracting 20% of the mass from the percentage. So basically (.20x+.60y=41.6)-.20(x+y=80)