3 birds were sitting on the fence. 6 more storks and 2 more birds came to join them. How many more storks than birds are sitting on the fence?
There are $x$ birds and $y$ storks sitting on the fence. 

The expression $(x+y)$ will be the total number of birds and storks, so we need to solve for this. 

We know that $x+y=9$ and that $y=2x-3$. We can plug this value of $y$ into our first equation to solve:

$$x+y=9$$
$$x+2x-3=9$$
$$3x=12$$
$$x=4$$

Now we have that $x=4$ and $y=2x-3=2(4)-3=5$.

There are 5 storks sitting on the fence.