In a certain code language, 'x' represents '+', '÷' represents 'x', '-' represents '÷' and '+' represents '-'. Find out the answer to the following question.
A mixture contains liquid A and liquid B in the ratio of 5 : 4. If 2 litres of liquid B is added to it, then the ratio of liquid A and liquid B becomes 7 : 6. What is the quantity (in litres) of liquid A in the mixture?