Question 708059
With values like those, you should guess that you'll need a bit more than  100ml of the 6.5%, and a bit less than 100 ml. of the 5 %.


x for 5% material, y for 6.5% material.

{{{(5x+6.5y)/200=6.0}}}
{{{5x+6.5y=1200}}}


Accounting for volumes to use, x+y=200.
You have a system:
{{{5x+6.5y=1200}}}
{{{x+y=200}}}


Multiply the second entire equation by 5, and subtract the result from the first....
Get  1.5y=200, so y=133 plus 1/3 milliliters
{{{y=133}}} ml. of the 6.5% acetic acid vinegar.


{{{x=67}}} ml. of the 5% material.