Question 1045066
Using arithmetic with a variable,
let v be how much of the pure 100% antifreeze to add.
{{{(2*10+100*v)/(v+2)=20}}}
Be sure this equation makes sense.  When it does, then a large part of the problem has been handled.  Solve for v.


{{{(2+v*10)/(v+2)=2}}}
{{{10v+2=2(v+2)}}}
{{{10v+2=2v+4}}}
{{{8v=2}}}
{{{highlight(v=1/4)}}}, which as quarts, would be 1 cup or 8 fluid ounces.