Find the prime factors of each denominator.

** 9 = 3 x
3
12 = 3 x 2 x
2
14 = 2 x 7
The LCD is equal to 3 x 3 x 2 x 2 x 7 = 252**

**Notice we took each prime factor the largest number of times it occurs
in any one
denominator not the total number of times it occurs in all the
denominators.**