6 birds were sitting on the fence. 4 more birds and 8 more storks came to join them. How many birds are sitting on the fence?
There are $x$ birds sitting on the fence. 
Then 4 more birds come, so there are $x+4$ birds sitting on the fence. 
Then 8 more storks come, so there are $x+4+8=x+12$ birds sitting on the fence. 

In conclusion, there are $x+12$ birds sitting on the fence.