In solving the problem related to ages, we come across three situations.
Always we consider the present age to be the base for finding out the past age or further age.
For example if the present age of a person is ‘Y’.
Age of the person after 10 year will be X+10.
Age of the person 10 year before would be x-10.
Present age of John is ‘25’.
Age of John after 10 year will be 25+10=35
Age of John Before 10 year would 25-10=15