The problem is asking to identify how many years would each color light last. We know that a red light turns on 50% of the time, a green light is 42% of the time, and yellow is 8% of the time. Each light lasts 100,000 hours.
Although this question gives a lot of information, we really don't need the percentages of the lights. They simply are there to throw you off. Each light lasts 100,000 hours. We will use the following conversions:
1 day = 24 hours
1 year = 365 days
100,000 hours divided by 24 hours = 4166.67 days
4166.67 days divided by 365 days = 11.4 years (the 4 is 4 months).