Answer:
Let x = ml of 21% solution
Let y = ml of 15% solution
ATQ,
x + y = 60.....(1)
or
0.21x + 0.15y = 0.6....(2)
Multiplying equation 1st by 0.21, we get,
0.21y+0.21y =12.6....(3)
subtracting equation 3
0.21y+0.21y =12.6
-0.21x +0.15y = 0.6
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ㅤㅤㅤ 0.6y = 12
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6y = 12
y = 20ml
x= 60-20 = 40 ml
Hence , Conner needs 20ml of 21% solution & 40ml of 15% solution