15 storks and 29 birds were sitting on the fence. 40 more birds came to join them. How many more birds than storks are sitting on the fence?
There are 15 storks and 29 birds sitting on the fence. 
40 more birds came to join them. 

So now we have a total of 40 + 29 = 69 birds sitting on the fence. 

There are 69 - 15 = 54 more birds than storks sitting on the fence.