Hello, annabananzaa!

These "mixture problems" can be solved if we organize our facts.How many liters of a 25% alcohol solution must be mixed with a 12% solution

to get 13 liters of a 15% solution.?

Let = liters of 25% solution.

Then = liters of 12% solution. (I hope you see why.)

The liters of 25% solution contains: . liters of alcohol.

The liters of 12% solutions contains: . liters of alcohol.

. . Hence, the mixture will contain: . liters of alcohol. .[1]

But we know that the final mixture will be 13 liters which is 15% alcohol.

. . It will contain: . liters of alcohol. .[2]

We just described the final amount of alcohol intwoways.

Thereis our equation! . . . Equate [1] and [2]

. . . .

Got it?