Analysis:

1. Circle six numbers with a rectangle of 2 times 3 on a month's calendar, and their sum is 69. What's the date of these six days?

1. Suppose these six days are A A+ 1 A+2 A+7 A+8 A+9 respectively.

A+A+ 1+A+2+A+7+A+8+A+9=69

A=7

So these six days are the 7th, 8th, 9th, 14, 15, 16 respectively.

2. The father is 40 years old and the son 12 years old. After _ _ _, the father is twice as old as his son.

2. set the year a.

(40+A)/( 12+A)=2

A= 16 years

Li Bin circled three adjacent numbers in a column of the calendar and calculated their sum, which is definitely wrong.

A.20 B.33 C.45 D.54

4. Xiao Zhao and Xiao Wang exchanged activities during the summer vacation. Xiao Zhao said, "I went to a week-long technology summer camp. The sum of the dates of these seven days is 84. Do you know what date I went out? " Xiao Wang said: "I went to my uncle's house for seven days during the holiday, and the date and number of months were also 84." Guess what date I went home? " Try and list the equations to solve the problem between Xiao Zhao and Xiao Wang.

4. Xiao Zhao went out on the 9th and Xiao Wang went home on July15th (hint: if the number of days in the middle of seven days is X, the other six days are X-3, X-2, X- 1, x+ 1, x+2 and x+3 respectively.