+658 Do you know how to convert from a base to base 10?
If so, I recommend you convert the numbers into base 10. Compute it. Then convert back into base 12.
If you do not know, I recommend to take a look again at your textbook or whatever online lesson you are taking. I am sure they have taught you the basics of base conversions and calculations.
There seems to be two variables in your expression. If that is all to the problem, the only thing I can think for you to do is express your answer in those two variables in base 12.
