Respuesta :
Since we mix 5 oz of 30% with 20 oz of 15%, then
Let us add 5 x 30% and 20 x 15%
[tex]\begin{gathered} 5\times\frac{30}{100}+20\times\frac{15}{100}= \\ \\ \frac{150}{100}+\frac{300}{100}= \\ \\ 1.5+3= \\ 4.5\text{ oz} \end{gathered}[/tex]This 4.5 oz has x concentration of the total amount 5 oz and 20 oz, then
we will multiply x by (5 + 20) and equate the answer by 4.5
[tex]\begin{gathered} (5+20)x=4.5 \\ 25x=4.5 \end{gathered}[/tex]Divide both sides by 25
[tex]\begin{gathered} \frac{25x}{25}=\frac{4.5}{25} \\ x=\frac{9}{50} \end{gathered}[/tex]Change it to percent by multiplying it by 100%
[tex]\begin{gathered} x=\frac{9}{50}\times100\text{ \%} \\ x=18\text{ \%} \end{gathered}[/tex]The percent of concentration is 18%
