The difference between the ages of two sisters Leela and Yamini is a variable.
Let Leela’s age be (L) years and Yamini’s age be (Y) years today.
Their age difference is:
( ext{difference} = |L - Y| )
After 1 year, their ages become:
( L + 1 ) and ( Y + 1 )
The new difference is:
( |(L + 1) - (Y + 1)| )
( = |L - Y| )
So the difference does not change with time. It stays the same every year.
Example: If Leela is 12 and Yamini is 9, the difference is:
( 12 - 9 = 3 )
Next year: ( 13 - 10 = 3 ) (still 3)