A three-digit number and ones

1. 10 less, 10 more than 300
2. Number detectives 235+6 = *
3. Addition Chains 100 + 5 + 5 + 7, 99 + 3 + 6 + 2
4. Beyond 100: 104 + 7
5. Beyond 110: 119+3
6. Beyond 120: 128+6
7. Beyond 130: 139 + 5
8. Changeover: 7 less than 301
9. Changeover: 6 less than 904
10. Changeover: 6 less than 503
11. Changeover: 7 less than 204
12. Changeover: 8 less than 305