2) How much PURE copper must be added to 50.255kg of an allow containing 12% copper to raise the copper content to 21%

let x=amt of pure copper to add:

12%*50+100%x=21%(50+x)

6+x=10.5+.21x

.79x=4.5

x=5.7

amt of pure copper to add: 5.7 kg

Step-by-step explanation:

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