Any odd integer can be expressed as 2n+1, for some integer n.
The next odd integer, after 2n+1, is 2n+1+2=2n+3
thus 9x=2n+1, means that 9x-1=2n, so n=(9x-1)/2
the next odd number after 2n+1 is 2n+3= 2* (9x-1)/2+3=9x-1+3=9x+2
Remark : this result could also have been found directly.
Answer: 9x+2