`1`

1. 12,24,36,48,60,72,84,96,108

2. 10,20,30,40,50,60,70,80,90

3. 7,14,21,28,35,42,49,56,63

4. 8,16,24,32,40,48,56,64,72

5. 5,10,15,20,25,30,35,40,45

6. 6,12,18,24,30,36,42,48,54

7. 11,22,33,44,55,66,77,88,99

8. 9,18,27,36,45,54,63,72,81

9. 3,6,9,12,15,18,21,24,27

10. 4,8,12,16,20,24,28,32,36

Mấy ảnh chị giỏi quá :D

 \(x - 7,2 = 3,9 + 2,5 \)

\( x - 7,2 = 6,4 \)

\( x = 6,4 + 7,2 \)

\( x = 13,6 \)