The correct sum is 623, not 513. Adding the ones gives 5 + 8 = 13, so write 3 and carry 1; the tens give 4 + 7 + 1 = 12, write 2 and carry 1; the hundreds give 3 + 2 + 1 = 6.

In the tens column, 5 + 3 = 8, not 7, so the middle digit must be 9 and the answer is 393. The ones and hundreds were already correct.

Adding the ones, 9 + 4 = 13, so write 3 and carry 1. Then 8 + 3 + 1 = 12 in the tens, write 2 and carry 1. Finally 4 + 2 + 1 = 7 in the hundreds, giving 723.

Line up the place values: 7 + 5 = 12 in the ones, write 2 and carry 1; 4 + 3 + 1 = 8 in the tens; 2 + 1 = 3 in the hundreds. The total is 382.

Starting in the ones, 8 + 4 = 12, so write 2 and carry 1. The tens give 6 + 1 + 1 = 8, and the hundreds give 3 + 2 = 5, making 582.

Add the ones first: 3 + 9 = 12, write 2 and carry 1. Tens: 5 + 2 + 1 = 8. Hundreds: 1 + 4 = 5. The sum is 582.

Ones: 6 + 8 = 14, write 4 and carry 1. Tens: 7 + 1 + 1 = 9. Hundreds: 2 + 5 = 7. That gives 794, with regrouping needed only in the ones place.

True. Since 7 + 5 equals 12, you cannot fit 12 in the ones column, so you write the 2 and carry the 1 over to the tens place.

False. Adding 321 + 456 column by column gives 7 ones, 7 tens, and 7 hundreds, so the actual sum is 777, not 787.

True. Four hundreds plus three hundreds is seven hundreds, just like 4 + 3 = 7. The tens and ones stay zero, so the sum is 700.