A metalworker has a metal alloy that is 15% copper and another alloy that is 65% copper. How many kilograms of each alloy should the metalworker combine to create 60kg of a 55% copper alloy?
Let x be the amount of the first alloy (15% copper) in kilograms.
Then, the amount of copper in the first alloy is 0.15x.
The amount of the second alloy (65% copper) is 60 - x.
Then, the amount of copper in the second alloy is 0.65(60 - x).
The total amount of copper in the final alloy is 0.55(60) = 33.
So, we have the equation 0.15x + 0.65(60 - x) = 33.
Simplifying the equation gives 0.15x + 39 - 0.65x = 33.
Combining like terms and subtracting 33 from both sides gives -0.5x = -6.
Dividing both sides by -0.5 gives x = 12.
Therefore, the metalworker should combine 12 kilograms of the first alloy and 60 - 12 = 48 kilograms of the second alloy to create 60kg of a 55% copper alloy. Answer: \boxed{12}.