Answer:
6x - 1 = 9
Step-by-step explanation:
1. first you have to divide every term in the equation by 2
  12x/2 + 4/2 = 20/2
2. simplify
  6x + 2 = 10
3. next you have to subtract one from both sides
  6x + (2-1) = (10-2)
4. simplify
  6x + 1 = 9