Respuesta :
we calculate the vinegar on 220 ml
[tex]\begin{gathered} 220\cdot\frac{7}{100} \\ =15.4 \end{gathered}[/tex]the dressing will have 15.4 ml of vinegar
now we can raise a sum
[tex]x+y=220[/tex]where X is the first brand and Y the second brand on ml
now the percent vinegar sum we know the result is 15.4 wich corresponds to 7%
[tex]\begin{gathered} x\cdot\frac{6}{100}+y\cdot\frac{11}{100}=15.4 \\ \\ 0.06x+0.11y=15.4 \end{gathered}[/tex]we have two unknowns and equations, so we can solve by any method.
i will solve y on the first equation
[tex]\begin{gathered} x+y=220 \\ y=-x+220 \end{gathered}[/tex]and replace on the second to find x
[tex]\begin{gathered} 0.06x+0.11(-x+220)=15.4 \\ 0.06x-0.11x+\frac{121}{5}=15.4 \\ -\frac{1}{20}x=15.4-\frac{121}{5} \\ -\frac{1}{20}x=-\frac{44}{5} \\ x=\frac{-44\times20}{5\times-1} \\ x=176 \end{gathered}[/tex]then replace x on any equation to solve y
[tex]\begin{gathered} x+y=220 \\ 176+y=220 \\ y=44 \end{gathered}[/tex]for each brand should she use x=176ml and y=44ml
