A family consists of father, mother, daughter and son. Their total age this year is 73. Father is 3 years older than mother, and daughter is 2 years older than son. Four years ago, the total age of family members was 58. How old is this family this year?

Four years ago, four people ***58,

Then four years later, according to common sense, it should be 58+4×4=74 years old.

But in fact, when I was 73,

In other words, my brother is 3 years old and was not born four years ago.

Sister 3+2=5 years old,

How old are mom and dad this year?

73-3-5=65 years old

Mom, this year

(65-3)÷2=3 1 year

Dad, this year

3 1+3=34 years old

A primary school organizes students of all grades to participate in math interest groups. There are 25 non-fourth-grade students, 26 non-fifth-grade students, and 33 students who participate in math interest groups in the fourth and fifth grades. How many students are there in the school math interest group?

There are 25 students who are not in grade four, and 25 students in grade 12356.

There are 26 students who are not in the fifth grade, and 26 students in the first, second, third and fourth grades.

* * * Those who have participated in school interest groups are

(25+26+33) ÷ 2 = 42 people