Daniel L. answered • 10/28/15

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Hi Liz,

If 10 liters of solution is 25% alcohol, then there are 0.25 x 10 = 2.5 liters of alcohol in it.

Now we're going to add X liters of water to make alcohol 15% of the new solution. . .

2.5/ (X + 10) = 0.15

Cross multiply--> 0.15 X + 1.5 = 2.5

Subtract 1.5 from both sides--> 0.15X = 1

Divide both sides by 0.15--> X = 6.67 liters

Check the answer by dividing 2.5 by 16.67 and see if you get 0.15 which is 15%

Have fun.

Dan