Can you circle a square in the calendar so that the sum of the four numbers in the square is 78? If so, what's the date of the four days? If not, please explain the reason,

Can you circle a square in the calendar so that the sum of the four numbers in the square is 78? If so, what's the date of the four days? If not, please explain the reason,

It is impossible to circle a square in the calendar so that the sum of the four numbers circled by the square is 78
reason:
Suppose you can circle a square in the calendar so that the sum of the four numbers circled by the square is 78
Note that the smallest of the four numbers is x, then the other three numbers are x + 1, x + 7, x + 8 in turn
The sum of four numbers x + X + 1 + X + 7 + X + 8 = 4x + 16 = 4 (x + 4) must be a multiple of 4
78 = 2 * 39 is not a multiple of 4
therefore
It is impossible to circle a square in the calendar so that the sum of the four numbers circled by the square is 78

Can you circle (2x2) numbers with a square in the calendar so that the sum of the four is 78? If so, what are the dates of the four days? If not, what are the dates of the four days

The number below must be 7 larger than the number above, and every two numbers are adjacent
Let the first number be x, then the following numbers are x + 1, x + 7 and X + 1 + 7 respectively
X + X + 1 + X + 7 + X + 8 = 78, x = 15.4 is not an integer, so it can't

On the calendar of a certain month, circle 2 times 2 arbitrarily with a square, and the sum of the 4 numbers circled is 100. What are the dates of these 4 days~

Let the first day be X
x+x+1+x+7+x+7+1=100
x=21
21, 22, 28, 29

In the calendar of a certain month, among the four numbers Xiao Gang circled with a square, the largest number is just twice the smallest number
What are the dates of these four days
In other words, I'm most afraid of meeting this kind of problem. I'm almost dead! If I want to list equations, I can still solve them if he says how much their sum is. But in this lesson in this unit, I'm the most speechless... I don't know what the relationship is, or I'm not good at this type of problem at all. I'm almost broken!
How to deal with this kind of problem! P. s: soon

Let the number of the upper left corner of a square be x, then the number of the upper right corner is x + 1, the number of the lower left corner is x + 7, and the number of the lower right corner is x + 8