Subtract 3-digit numbers
1 Subtract 3-digit numbers: no regruoping 
2 Subtract: regroup tens
3 Subtract: regroup hundreds
4 Subtract 3-digit numbers: regrouping
5 Check-up (1) 
6 Word problem (1)
7 Word problem (2)
8 Word problem (3)
9 Check-up (2)
10 Check-up (3)