let the weight of the second alloy be y
convert the percentage to fraction, that is 10/100=0.1, 18/100=0.18, 13/100=0.13
Total weight if the mixture is 0.1 x 25+0.18y=0.13(25+y)
2.5+0.18y=3.25+0.13y
like terms together
0.18y +0.13y = 3.25-2.5
0.05y=0.75
divide both side by 0.05
Y is therefore 15 pound of 18% copper is needed
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Answer:

Step-by-step explanation:
The equation of a circle of radius r, centered at the point (a,b) is

We already know the center is at
, we are just missing the radius. To find the radius, we can use the fact that the circle passes through the point (7,4), and so the radius is just the distance from the center to this point (see attached image). So we find the distance by using distance formula between the points (7,4) and (4,-5):
radius
And now that we know the radius, we can write the equation of the circle:

