Answer
$980$
Work Step by Step
$621 + 359$
Start at the right of each number and add the ones digits
$1 + 9 = 10$ ones
Regroup the 10 ones as $1$ ten and $0$ ones
Write the $0$ one in the ones column.
Write the $1$ ten in the tens column.
Add the tens digits next including the regrouped $1$.
$1 + 2 + 5 = 8$ tens
Write the $8$ tens in the tens column.
Add the hundreds column next
$6 + 3 = 9$ hundreds
Write the 9 hundreds in the hundreds column
The sum of the two numbers is $980$