1. Thursday - My first step was to find what mod of 7, 31 was. 31/7=4R3. Next, I added 3 days to Monday because 31 is not a multiple of 7. The remainder of 3 is the same as adding 3 days to Monday.
2. Saturday - First, I found the number of days there were until Christmas, from April 1st. Next, I divided the difference between the two dates, with seven and got a remainder of 2. The remainder is the same as the mod. I found the weekday 2 after Thursday, which was Saturday.
3. Monday – When you are getting from one day to the exact same day, but the next day, you need to know how many days are in between. In this case, it is a leap year with 366 days. I divided 366 by 7. The answer is 49 mod 3. Next, I added 3 days to Friday and ended up on Monday.
4. Wednesday – My birthday is on December 1. Like I solved the other problems, I found the difference between today’s date and my birthday. Next, I used that to find 216 (amount of days until my birthday) mod 7. The remaining was added on to today's day, Thursday, May 6th, and I found out that my birthday is on a Wednesday.