When you are adding or subtracting fractions, always find a common denominator first or you cannot add them or subtract them.
When you are multiplying fractions, you can just multiply. You do not have to worry about finding a common denominator.
When you are dividing fractions, keep the first fraction the same. Then, change the division to multiplication. Always keep in mind that when you are dividing fractions, you are actually multiplying. The last step of dividing fractions is to flip the second fraction to the opposite of what it is. Do not change the sign though.
An example of this is if you had the problem 1/2 divided by 2/3. Your math would look like this:
1/2 / 2/3
1/2 * 3/2
3/4 is the answer
I hope that this helps :)