Question: James buys 3 CDs. Two of them are 1.5 hours each. The last one is twice that long. What is the combined length of the CDs?
Answer with step-by-step thinking: The long CD is 1.5 * 2 = 3 hours. The two shorter CDs have a combined length of 1.5 * 2 = 3 hours. So in total the CDs had a length of 3 + 3 = 6 hours.
So the answer is 6.

Question: If one fourth of the engines are defective, and there are 5 batches of 80 engines each. How many engines are not defective?
Answer with step-by-step thinking: There are 80 * 5 = 400 engines in total. 400 / 4 = 100 of the engines are defective. 400 - 100 = 300 of the engines are not defective.
So the answer is 300.

Question: Lily types 15 words a minute and takes a 2-minute break every 10 minutes. How long does it take for Lily to type 255 words?
Answer with step-by-step thinking:
It would take Lily 255 words / 15 wpm = 17 minutes to type without taking a break. Since Lily takes a break after 10 minutes of typing she takes 17 minutes + 2 minutes = 19 minutes.
So the answer is 19.