You can combine the same numbers with the same variables using the operation sign for each. For example, using your equation, you would combine the 3n and 4n which is 7n. So your equation would be 7n - 2
Combining like terms means that if u have two terms that are the same coefficient like 3n and 4n you have to either add or subtract because You have to have only one n in one side so u add 3 to 4 and u get 7n. Another example: 3n-2= 4n you would have to the same thing which is to add both. I'm sorry I'm not the best at explaining
