For the following questions answer them individually
If '$$+$$' means'$$-$$', '$$-$$' means'$$+$$', '$$\times$$' means'$$\div$$' and '$$\div$$' means'$$\times$$' , then which of the given equations is correct ?
Father's age at the time of the birth of his son was the son's present age. If the son's age is 20 years, then find the father's present age.
An article costing Rs.1000 is sold at 5% loss and another article purchased with the money got was again sold at 5% gain. Was there a loss or gain and how much?