One can transcribe the description exactly as written,
here using w for the whole quantity of mixture.
Copper (w/2)-16
Tin (w/3)-12
Lead (w/4)+4
WHOLE w
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Another way, the whole mixture is some 12 equal parts, so 12M is this mixture quantity.
Copper 6M-16
Tin 4M-12
Lead 3M+4
WHOLE 12M
Remember M here is a factor.
Equation to solve can be .
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