Question: 18x + 5 - 7x - 9

Answer: 11x - 4

Question: 5m - 17 - 5 + 2m

Answer: 7m - 22

Question: 20 - 10y - 7y +9

Answer: -17y + 29

Question: -15k - 1 + 12 + 2k

Answer: - 13k + 11

Question: 12x - 13 - x - 9 + 10x

Answer: 21x - 22