Sederhanakanlah! 1 per 2 (2a – 4b) – 1 per 3 (6a + 9b)

1/2 (2a-4b) – 1/3 (6a+9b) =
2/2 a – 4/2 b – 6/3 a + 9/3 b
= a – 2b – 2a + 3b
= -a + b