Answer
7,999
Work Step by Step
Step 1: Add ones column
6, 3 4 4
+ 1, 6 5 5
_________
9
Step 2: Add tens column
6, 3 4 4
+ 1, 6 5 5
_________
9 9
Step 3: Add hundreds column
6, 3 4 4
+ 1, 6 5 5
_________
9 9 9
Step 4: Add thousands Column
6, 3 4 4
+ 1, 6 5 5
_________
7, 9 9 9
The sum of the three numbers is 7,999.