Answer: C
Step-by-step explanation:
21x+9-3x = 18x + 9
If you factor out the 9, you would be left with
9 (2x+1)
Answer: A. 9(2x - 1)
Step-by-step explanation:
combine like terms
21x+9-3x
21x-3x
18x+9
Factor the expression
factor out 9 from the expression
you get 9(2x - 1)