When adding larger numbers together you can use column addition. First you line the ... with the two numbers organised in columns according to the place value of each digit. 17 has 1 group of ...

If you can add two 3-digit numbers ... example, 345 + 129 is the same as 129 + 345. Look out for these key words in problems: 'total', 'sum', 'altogether', 'more'. They all indicate an addition ...