Answer:
(A)129 Pounds
Explanation:
Let x be the number of 23% zink alloy
Therefore:
Since the total result is 516 pounds
The number of pounds of 42% zink alloy =516-x pounds
We then have the resulting equation:
0.23x+0.42(516-x)=0.3725*516
0.23x+216.72-0.42x=192.21
Colect like terms
0.23x-0.42x=192.21-216.72
-0.19x=-24.51
Divide both sides by 129
x=129 pounds
Therefore, the number of pounds of 23% zink alloy that must be mixed is 129 pounds.