How could you keep an objects acceleration the same if the force acting on the object were double?

You can keep an object's acceleration constant if the force acting on it is double by adding another force going in the opposite direction of the first force. The second force will have to be as strong as the first force was originally in order for the acceleration to be the same. This is the same concept as if you have 2 of something, double it to get 4, and subtract 2 again. You'll end up with the same value you started with.