w birds were sitting on the fence. x more storks and y more birds came to join them. How many more storks than birds are sitting on the fence?
w - the number of birds sitting on the fence
x - the number of storks that came
y - the number of birds that came

w + x - y = the number of storks that are sitting on the fence

There are more storks than birds on the fence if:

w + x - y > 0 
w + x > y