Question 947840
A 40% solution would have 40 liters of vinegar and 60 liters of water. 
{{{(40)/(40+60)=40/100=0.4}}}
An 80% solution with 40 liters of vinegar would have 10 liters of water.
{{{(40/(40+10))=4/5=0.8)}}}
You need to evaporate 50 liters of water.
{{{60-10=50}}}