(the ^ is for the exponent by the way and the / is for the fraction sign).
First you would reduce the problem with the b's. (cross them out) so now you have 12a^3c^4/3ac^2.
Then divide the 12 by 3, reduce that and cross out the three. So now you have 4a^3c^4/ac^2
Reduce the A. (cross em out) so you have 4a^2c^4/c^2
Then cross out the c^4 and c^2. Now you get 4a^2c^2 and that is your answer.
