Hi, need help for the following question on quadratic equation:

A beaker has 400 cubic centimetres of water. V cubic centimetres of water is poured out and then replaced by the same amount of vinegar.  After stirring well, V cubic centimetres of the first mixture is poured out and replaced by the same amount of vinegar again. The percentage of vinegar in the final mixture is 36%. Find the value of V. 

Thanks. 

Source: ?