5. In September 2014, when they started the first grade, all students in 5.a grade together had 153 years, and in September 2018, at the beginning of the fifth grade, those same students had a total of 245 years. How many of them started school at six, and how many at seven years old?

Each task is scored out of 10 points.

The use of a pocket calculator or any manuals is not allowed.
First method:

From September 2014 to September 2018, 4 years have passed.

1 POINT

During this time, the total number of years of all students increased by

$245-153=92$ years.

2 POINTS

Since each student aged 4 years, there are

$92: 4=23$ students in the class.

2 POINTS

If all students started the first grade at 7 years old, they would have a total of $7 \cdot 23=161$ years.

2 POINTS

Since they had 153 years, then 6-year-olds started school

$161-153=8$ students.

2 POINTS

Then, 7-year-olds started school $23-8=15$ students.

1 POINT

TOTAL 10 POINTS