Question

mary is twice older than her sister.in 5 years time,she will be 2 years older than her sister.find how old are they both now

Answer 1

Let Mary's sister's age = n, then Mary's age = 2n.
After 5 years, Mary's age = 2n+5, and Mary's sister's age = n+5.
(2n+5) is greater than (n+5 ) by 2.
Hence (2n+5) = (n+5) + 2 ==> n = 2.
Hence Mary is 4 yrs old and her sister is 2 year old.