1/3 and 1/4 =12 what is the common denominator?

The common denominator would be 12 because 3*4=12 and 4*3=12

The common denominator would be 12 because 4x3=12 and 3x4=12
In order to find the common denominator, you need to find the least common multiple (LCM).
3:3,6,9,12,15,18,27,24,27
4:4,8,12,16,20,24,28,32, 36
They both have 12 and 24 but we are looking for the LEAST common multiple so it is 12 (since 12 is the first number that 4 and 3 can make together. That is what the LCM is)