Official Solution:If John is 3 years older than Jennifer, how many years ago was John twice as old as Jennifer? Let the ages of John and Jennifer be denoted by \(x\) and \(y\) respectively. We're looking to determine a value \(n\) such that \(x - n = 2(y - n)\).
(1) The combined age of John and Jennifer is 59 years.
This statement implies that \(x + y = 59\). Together with the equation \(x = y + 3\) from the stem, we have two distinct linear equations with two unknowns; hence we can solve for both \(x\) and \(y\), substitute into \(x - n = 2(y - n)\), and solve for \(n\). Sufficient.
(2) Eleven years ago, John was 20 years old.
The above implies that \(x - 11 = 20\), which gives \(x = 31\) and thus \(y = x - 3 = 28\). Substituting these values into \(x - n = 2(y - n)\) gives \(31 - n = 2(28 - n)\), which results in \(n=25\). Sufficient.
Answer: D