What is the difference between the energy of spring a, stretched 0.6 meters, and spring b, stretched 0.3 meters, if they have the same spring constant?

delE = 1/2 k (dX^2 - dx^2); where dX = .6 m and dx = .3 m.  

So we need k, the constant, to get the "difference."  

But I'm guessing you really want E/e = 1/2 kdX^2/1/2 kdx^2 = (dX/dx)^2 = 4 so E = 4e, which is to say spring A has 4 times more energy than B. ANS.

Spring A has more potential energy than spring B.

measuring things 1 litre of water