Question 883743
The description feels clumsy.  Fraction concentration volume for volume seem more neat to use, for me, anyway.


The milk mixture needed was to be {{{3/5}}} milk in water.  What was actually delivered was 8 liters of {{{2.5/5}}} milk in water.  Maybe one would not like the use of rational looking numbers with non-integer part:  Then we can also say,


Milk Mixture wanted:  6/10.
Milk Mixture received:  5/10.


Add some milk, v liters, to the 8 liters of less concentrated mixture.


Form this equation (as the reasoning for it is omitted):
{{{highlight_green(highlight_green((8(5/10)+v)/(v+8)=6/10))}}}
and simplification should be performed
{{{(8(1/2)+v)/(v+8)=3/5}}}
{{{(4+v)/(v+8)=3/5}}}
{{{5(4+v)=3(v+8)}}}
{{{5v+20=3v+24}}}
{{{2v=4}}}
{{{highlight(v=2)}}} liters of milk to add.