Question 551616
Alloy A
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Amount = x 
Concentration =100% =1 (It is pure copper so concentration will be 100%)


Alloy B
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Amount = 132-x
Concentration =12% = 0.12


Resultant Alloy
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Amount =132 
Concentration =20%=0.2


[Amount Alloy A * Concentration A] + [Amount Alloy B * Concentration of B] = Amount of Resultant * Concentration of resultant
(x)(1)+(132-x)(0.12)=(132)(0.2)
x+15.84-0.12x=26.4
0.88x+15.84=26.4
0.88x=2.64-15.84
0.88x=10.56
0.88x/0.88=10.56/0.88
x=12



Alloy A
--------
Amount = x = 12kg 
Concentration =100% =1 (It is pure copper so concentration will be 100%)

Alloy B
-------
Amount = 132-x = 132-12 = 120kg
Concentration =12% = 0.12


12kg of pure copper and 120kg of 12% alloy will be used to produce 132 kg of the 20% alloy.