2. Tina wrote down one natural number on each of five pieces of paper, but she didn't want to reveal which numbers she had written. Deleted Žan managed to convince her to tell him all the sums of pairs of numbers. He found out that the sums were 17, 20, 28, $14, 42, 36, 28, 39, 25$ and 31. Which numbers did Tina write down?
I/2. Let's denote the numbers by $a, b, c, d$ and $e$. We can assume that $a \leq b \leq c \leq d \leq e$. Arrange the sums in order: $14, 17, 20, 25, 28, 28, 31, 36, 39, 42$. It is clear that $a+b=14$, $a+c=17$, $d+e=42$, and $c+e=39$. If we add all the sums, each number appears exactly four times in this sum, so $4(a+b+c+d+e)=280$ or $a+b+c+d+e=70$. Since $a+b=14$ and $d+e=42$, it follows that $c=14$. Now it is not difficult to find the other four numbers, so the solution is: $3, 11, 14, 17, 25$.