What is the round to the biggest place value for 613
42,398
68,765
20,799
and how you calculate it i'm trying to my son

This makes no sense in sorry.

To round 613 42,398 68,765 20,799 you first have to look at the second digit and 3rd digit for the number. If it is 4 or less round down if it is 5 or more round up. For example for 613 you would round it to 610. On 42398 you round it to 42000. For 68765 you would round to 69000, On 20799 you would round to 21000. I hope this helped you out and your son.