To add with Unlike Denominators you must follow these steps.
1)Find the common denominator but it must be the LCM (Lowest Common Multiple).
A Multiple- Is the product of any given number and natural number like 1,2,3.
eg. Multiple of 3 are ; 3,6,9,12,15,18,21 etc.
Multiples of 2 are 2,4,6,8,10,12,14,16,18 Multiple of 5 are 5,10,15,20,25,30,35,40
You can't add that, so you have to find the common multiple .
Multiple of 4- 4,8,12,16,20,24,28,32,
Multiple of 6 - 6,12,18,24,30,36,4212 is the common multiple between those numbers.
The next step is to put " 12"(in this case) The new denominator and whatever you multiply in the bottom, you must do in the top.
The last step is to add it all up.