## Task 2 - 230612

One brigade bought three books and two balls for their patron class. Another brigade bought three books and four balls. All books cost the same amount. All balls also cost the same amount. The first brigade paid 15 marks, the second brigade paid 24 marks.

How many marks did a book cost? How many marks did a ball cost?
The second brigade bought exactly two more balls and paid (due to 24 - $15=9$) exactly 9 marks more than the first brigade. Consequently, a ball costs (due to $9: 2=4.50$) exactly 4.50 marks.

Thus, the first brigade paid exactly 9 marks for the balls. Due to 15 - $9=6$, she paid exactly 6 marks for the three books, so a book costs exactly 2 marks.