(Sorry if this is a stupid question)

Suppose the purpose of the case is to improve a metric like cost/revenue/profits/time quantitatively, for instance:

1. How will you help our client increase 50% profits by next year?

2. Reduce costs by 25% by next 2 years

What is the correct way to reach a solution in either case? 

I understand that the answer would be based off the data provided to the candidate at the time, but which resulting metric would be considered the best answer in both cases? 

Could some of those metrics be penetration rate/CAGR/profit margins in case of increasing revenue/profits?

What about costs? 

Thank you so much for any kind of guidance in advance!