Q: A store owner repacked his oils into 200 mL bottles. He was able to make 20 bottles. How many liters of oil did the store owner have?
A: Twenty bottles of oil is equal to 200 mL x 20 = 4000 mL. Since 1 liter is equal to 1000 mL, then the store owner had 4000 / 1000 = 4 liters of oil. The answer is 4.

Q: If there were 200 students who passed an English course three years ago, and each subsequent year until the current one that number increased by 50% of the previous year's number, how many students will pass the course this year?
A: We begin 3 years ago with 200 students, and moving forward to two years ago we find there were 200 * 1.5 = 300 students who passed. At the end of the subsequent year 50% more students pass than last year's 300, so that means 300 * 1.5 = 450 students pass. At the end of the current year there's another 50% increase over the previous year, meaning we have 450 * 1.5 = 675 students pass. The answer is 675.

Q: Ashley had a birthday party and invited 20 of her friends, telling them to each invite one more person to attend the party. If half the number of the invited guests each came with one more person, what's the total number of people at the party, including Ashley?
A:
If she invited 20 friends, then the number of friends who came with one more person is 1 / 2 * 20 = 10. If the 10 friends came with 10 more people, the total number of guests becomes 20 + 10 = 30 guests. If you add Ashley, the total number of people in the party is 30 + 1 = 31 people. The answer is 31.