A 13 L solution that was 12% vinegar was mixed with a 9 L solution that was 70% vinegar. What is the concentration of the new mixture?

The concentration is simply 36%

Step-by-step explanation:

In this question, we are concerned with calculating the concentration of a new mixture formed from mixing some liters of each of two vinegar variants of different concentrations.

We proceed as follows;

The concentration of the new solution will contain 12% of 13L vinegar A and 70% of 9L vinegar B

13L of vinegar A will contain 13 * 12% = 13 * 0.12 = 1.56

9L of 70% vinegar B will contain 9 * 70% = 9 * 0.7 = 6.3

Now, the new mixture has a total volume of 13 + 9 = 22L

The concentration of the new mixture will thus be;

(1.56 + 6.3) / 22

= 0.357 and that's approximately 0.36 or simply 36%