2 3 4 1 1. + = 2. + = 7 7 9 9 5 3 2 1 3. + = 4. + = 11 11 4 4 4 1 3 2 5. + = หรอ 6. + = ื 5 5 8 8 6 5 11 4 7. + = 8. + = 12 12 17 17 3 4 13 4 9. + = 10. + = 10 10 20 20