Can a rocket be taken to the edge of space with balloons so it can fly from there? Can we have a (I assume very large) airship or balloon to take a rocket ship all the way to the upper atmosphere so it can use a lot less fuel from there to go to space/other planets. We could even have fuel taken up there using the balloon in order to refuel many rockets on their way to space. Would this be viable?
Assuming a lift force of around 5.28 kN and rocket empty mass of  25,600 kg
 A: Getting to orbit is not really a matter of height. It's a matter of speed. You need extremely high sideways velocity (10,000+ mph) to achieve orbit without simply falling back to the ground. The fastest we know how to propel any vehicle is using rockets. And since we are already building the rocket for the purpose of speed, it's best to also use the same rocket propulsion to get the initial height off the ground. In fact, height is required mainly because it's impossible to achieve 10,000+ mph speeds in the thick atmosphere without burning up your ship like a meteor.  But height (altitude) is not the main difficulty in space travel. In fact, on the Moon it's possible to fire a projectile horizontally from the surface and have it achieve orbit, because of the lack of atmosphere.
I think you would benefit from looking up Newton's Cannonball.
With all that said, the company Virgin Galactic is working on launch platform that fires a small rocket from a high altitude plane, not entirely dissimilar to your balloon concept. The problem with balloons is they cannot carry very much weight for a given size.
