Add 2-digit numbers: regrouping
1 Add 1-digit numbers and 2-digit numbers: no regrouping 
2 Add 2-digit numbers: no regrouping 
3 Add 1-digit numbers and 2-digit numbers
4 Add 2-digit numbers to 30
5 Add 2-digit numbers to 60
6 Add 2-digit numbers to 99
7 Check-up (1) 
8 Add three numbers
9 Word problem: add 2-digit numbers (1)
10 Word problem: add 2-digit numbers (2)
11 Check-up (2)
12 Check-up (3)