Answer:
The percentage of fat in the mixture is 8%
Step-by-step explanation:
Let
x -----> the percentage of fat in the mixture
we know that
The volume of milk multiplied by its percentage of fat plus the volume of cream multiplied by its percentage of fat must be equal to the total volume of he mixture multiplied by the percentage of fat in the mixture
Remember that
15%=15/100=0.15
3%=3/100=0.03
so
[tex]5(0.15)+7(0.03)=(5+7)(x)[/tex]
Solve for x
[tex]0.75+0.21=12x[/tex]
[tex]0.96=12x[/tex]
[tex]x=0.08[/tex]
Convert to percentage
[tex]0.08*100=8\%[/tex]