Problem 3. On a board, Zoran and Petar wrote two numbers. Zoran wrote a three-digit number which has the digit in the units place 1, the digit in the tens place which is 3 times larger than the digit in the units place, and the digit in the hundreds place which is 3 larger than the digit in the units place. Petar wrote a number which is the predecessor of the largest odd number from the first ten of the second hundred. Sanja added the written numbers, and then reduced the sum by their difference. What number did Sanja get?
Solution. Zoran wrote down the number 431. Petar wrote down the number 108. And Sanja calculated as follows: (431+108)-(431-108)=539-323=216.