184 milliliters of the first brand and 46 milliliters of the second brand
Step-by-step explanation:
Step 1:
Let x be the number of milliliters of the first brand in the final mixture
Since the chef requires 230 milliliters, 230 - x would be the milliliters of dressing of the second brand
Step 2:
The first brand contains 6% vinegar, and the second brand contains 11% vinegar
Hence we have,
x * 6/100 + (230-x) * 11/100 = 230 * 7/100
0.06 x + 25.3 - 0.11 x = 16.1
0.05x = 9.2 => x = 184
Hence the 184 milliliters of the first brand is to be used
Step 3 :
Quantity of the second brand to be used is 230 - x = 230 -184 = 46 milliliters.