college math
posted by Devan .
Base Twelve.
B08twelve + ? = 9twelve

So is your question using base twelve, 08+?=9
or is it
Base eight, 12 + ?= what in base 12?
I have no idea what your question is 
Are you supposed to work your arithmetic within the base 12 ?
If so, then you should have an addition table, which you can use also for subtraction
Other option:
switch the numbers to base 10, do the arithmetic, then switch back.
B08twelve + ? = 9twelve
(11(12^2) + 0(12) + 8) + ? = 9
1592 + ? = 9
the missing number is 1583
which in base 12 = AB1
to work within the base
B08
 9 I will have to borrow, all the way from the B

AB1