Find the first four common multiples of the following : 

$3$ and $4$.

Multiples of $3=3,6,9,12,15,18..$
Multiples of $4=4,8,12,16,20..$

The first common multiple will be $12$

And the next common multiples will be multiples of $12$

Hence, first four common multiples of $3,4$ are $12,24,36,48$