In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.
One example: A lion has _ legs.
Solution is here: four
Explanation: The most logical numeric answer in words is four.

Now, solve this: Fluorescent lights are _ to four times more energy-efficient.
Solution:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
three