I studied for four hours. I added 2 more hours every day for a week. How many more days do I have to study until I have spend 20 hours studying?

you have an arithmetic series:

4 + 6 + 8 + ...
Easy to see that after 3 days, you will have already spent 18 hours,
so you need one extra day of only 2 more hours to have a total of 20 hrs.

To solve this problem, let's break it down step by step:

1. Start by calculating the total number of hours studied for the first day. You studied for four hours on the first day.

2. Next, calculate the additional hours you studied each day for a week. You added 2 hours each day, so for a week (7 days), you added a total of 2 hours x 7 days = 14 hours.

3. Now, add the initial four hours and the additional 14 hours studied over the week: 4 hours + 14 hours = 18 hours.

4. Finally, subtract the total hours studied (18 hours) from the desired number of hours studied (20 hours). 20 hours - 18 hours = 2 hours.

Therefore, you still need to study for 2 hours to reach a total of 20 hours.

Keep in mind that this calculation assumes you are studying the same number of hours each day over the week. If your study schedule changes each day, you would need to provide the specific hours for each day to get an accurate answer.