Age problem: Sara is 5 years older than jhane. Darsi is twice as old as Jane. The sum of the ages of the three girls is 65. How old is each? Prove your answer.

Let j represent Jane's age. The sum of ages can be written as
  (j + 5) + (2j) + j = 65
  4j = 60    (subtract 5)
  j = 15    (divide by 4)

Jane is 15. Sara is 5 years older, so is 20. Darsi is twice as old, so is 30. The sum of their ages is 15 + 20 + 30 = 65.