Answer:
She should mix <u>20 ounces</u> of 16% solution and <u>12 ounces</u> of 8% solution.
Step-by-step explanation:
Given:
Doreen Schmidt needs to prepare 32 ounces of a 13% hydrochloric acid solution.
Now, to find the amount she should mix of 16% solution and of 8% solution.
Let the 16% solution amount be 
And let the 8% solution amount be 
<em>So, the total ounces of solution:</em>

.......(1)
Now, to solve the equation to get the solution she should mix:


Substituting the value of
from equation (1) we get:



Subtracting both sides by 2.56 we get:

Dividing both sides by 0.08 we get:

<em>The 16% solution amount = 20 ounces.</em>
Now, substituting the value of
in equation (1) we get:

<em>The 8% solution amount = 12 ounces.</em>
Therefore, she should mix 20 ounces of 16% solution and 12 ounces of 8% solution.