A math problem for three years in primary school: add up all the dates of Wednesdays in a month, and the sum is 66. What day is the first day of this month? I know the answer is Friday, but I don't know how to try What should I tell him

A math problem for three years in primary school: add up all the dates of Wednesdays in a month, and the sum is 66. What day is the first day of this month? I know the answer is Friday, but I don't know how to try What should I tell him

The dates of the four Wednesdays of each month are 7 in turn
The last three Wednesdays were 7 14 21 larger than the first in turn
Then 66-7-14-21 is four times the date of the first Wednesday
The first Wednesday is (66-7-14-21) / 4 = 6
The first is 3 + 7 - (6-1) = 5, Friday

If the 3rd of a month is Wednesday, what day is the 30th of this month
Please list the formula and make it more specific,

30-3=27
27÷7=3…… six
6+3=9
9-7=2
The 30th is Tuesday

January 1, 2008 is Tuesday, so the 28th of this month is Xiao Ming's birthday. What day is it? How to explain primary school math problems to children?
Ask for detailed explanation

January 1st is Tuesday. So every seven days is Tuesday
So the 29th was Tuesday
So the 28th is Monday

The experimental primary school has a holiday on July 4, 2012, which is Wednesday. It starts on September 3, 2012, which is the day of the week

Monday