In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?
Six year ago Parvez’s age was same as the present age of Manish. If the present age of Parvez is one-fourth more than that of Manish's present age, then in how many years will Parvez’s age become double of Manish’s present age?