A2. Lucijana chose 3 different numbers from the set $\{1,2,3,4,5,6,7,8,9\}$. With these, she wrote the largest possible three-digit number and the smallest possible three-digit number. She added the obtained numbers and got the number 545. What is the sum of the 3 numbers that Lucijana chose?
(A) 6
(B) 7
(C) 9
(D) 11
(E) 13
A2. Let $a, b$, and $c$ be the numbers chosen by Lucijana, with $a > b > c$. The largest possible number that can be written with them is $\overline{a b c}$, and the smallest possible number is $\overline{c b a}$. For their sum, it holds that $100 a + 10 b + c + 100 c + 10 b + a = 101(a + c) + 20 b = 545$. By comparing the units on both sides of the equation, we see that $a + c = 5$ or $a + c = 15$, and by comparing the hundreds on both sides of the equation, we see that $a + c = 5$. Therefore, $b = 2, a = 4$, and $c = 1$, and $a + b + c = 7$.