1. Mom works for 3 days and has a rest 1 day, and Dad has a regular rest on Saturday and Sunday, so just find out the question "Mom's rest day happens to be Saturday or Sunday". On Sundays, 10, 15, we rest every four days 1 day, so on Thursdays,15+4 =19; Continue down, 19+4=23, Monday; 23+4=27, Friday; 27+4=3 1, Tuesday; 3 1+4-3 1=4, Saturday (already 1 1 month); So the next synchronized break is: 20061Saturday, October 4th 165438.

2.2 The average year is at least 28 days and the leap year is at most 29 days. The title also says "there are three groups of students", "the number of students in each group is not equal" and "no one comes alone" (note: the title gives these three conditions, and all three must be met at the same time). Suppose there are two people in one group, then there are three people in the other two groups with the least number of students. Only in this case, because 2×3×5 or even 2×3×6 does not match the following situations. So, a * * * came with nine students. (2+3+4=9)

By the way, children's shoes upstairs, please don't confuse people with children, please see the problem clearly!