Chapter 1 - Whole Numbers - 1.2 Adding Whole Numbers - 1.2 Exercises - Page 18: 3

$56+33=89$

First, add the digits in the ones column (each number's ones place) to determine the digit in the ones place of the sum: $6+3=9$ Next, add the digits in the tens column (each number's tens place) to determine the digit in the tens place of the sum: $5+3=8$ If the sum has $8$ in the tens place and $9$ in the ones place, it must be $89$.