Achef is going to use a mixture of two brands of italian dressing. the first brand contains 9% vinegar, and the second brand contains 14% vinegar. the chef wants to make 230 milliliters of a dressing that is 13% vinegar. how much of each brand should she use?

So, the first brand has 9% vinegar, and say we use "x" amount of it, then, the amount of vinegar in "x" is 9% of x, or (9/100) * x, 0.09x.

the second brand has 14% of vinegar, and if we use say "y" amount of it, then the amount of vinegar in "y" is really just 14% of "y" or, (14/100) * y, 0.14y.



so, whatever "x" and "y" are, we know that x + y = 230.

and we also know that their concentration amounts will also add up,  0.09x + 0.14y = 29.9.



how many milliliters will it be for the second brand?  well, y = 230 - x.