Thank you for the answer. Reviewing my answers to Oliver Lehmann's test now and could not figure this one out. His site and test has been pointed out as a great source: http:/www.oliverlehmann.com/pmp-self-test/75-free-questions.htm.
The formula used is the formula to calculate the percentage value
Percent Change = (New Value - Old Value) × 100%
Also hoping the real questions are not this tricky. Can't afford to spend 5 mins in one question..