(a) Add ones: 2 + 7 = 9. Add tens: 3 + 4 = 7. Answer: 79 (b) Add ones: 4 + 5 = 9. Add tens: 5 + 9 = 14, write 4 carry 1. Add hundreds: 6 + 1 = 7. Answer: 749 (c) Add ones: 6 + 3 = 9. Add tens: 8 + 2 = 10, write 0 carry 1. Add hundreds: 2 + 1 + 1 = 4. Answer: 409 (d) Add ones: 6 + 4 = 10, write 0 carry 1. Add tens: 7 + 2 + 1 = 10, write 0 carry 1. Add hundreds: 4 + 3 + 1 = 8. Answer: 800 (e) Add ones: 0 + 9 = 9. Add tens: 0 + 8 = 8. Add hundreds: 7 + 2 = 9. Answer: 989 (f) Add ones: 4 + 3 = 7. Add tens: 3 + 8 = 11, write 1 carry 1. Add hundreds: 5 + 4 + 1 = 10. Answer: 1017