Answer:
• First brand: 70 milliliters
,• Second brand: 140 milliliters
Explanation:
• Let the volume of the first brand used = x mL
Since the volume of dressing the chef wants to make is 210 mL:
• The volume of the second brand = (210-x)mL
This gives rise to the equation:
[tex](6\%\text{ of x)+}(9\%\text{ of (210-x))}=8\%\text{ of 210}[/tex]Next, solve for x:
[tex]\begin{gathered} 0.06x+0.09(210-x)=0.08\times210 \\ 0.06x+18.9-0.09x=16.8 \\ 0.06x-0.09x=16.8-18.9 \\ -0.03x=-2.1 \\ x=\frac{-2.1}{-0.03} \\ x=70mL \end{gathered}[/tex]Thus, for the first brand, he should use 70 mL.
For the second brand, he should use (210-70) = 140 mL.