[Samildanach]

Infinity is NOT a number its a concept more or less meaning ENDLESS.
Every number in itself has the property of an infinity associated with it. For example the number we round to 1 is really 1.0000000 endless string of zeros. Infinities do not have to be variables although they can be eg pi which is infinitely variable as far as we know but they do not have to be.
So really even doing a normal equation such as one plus one is adding two infinities, proving that infinities can be added and subtracted and multiplied and divided.
In classical math anything dived by infinity is approximated to zero. Comrade is quite correct that 1/infinity = 2/infinity. As the difference between them will be impossible to measure. Anything that you can not measure a difference between might as well be the same thing. Autolykos is also theoretically correct because there will be a difference albeit a negligible one.
Thats if you use the mathematical concept of infinity which is an ever increasing positive number.
However consider an infnitiy thats starts at zero and moves in both the x and -x direction. Every increment along the x axis would be cancelled by the -x axis so you would effectively be dividing by 0.
Most of all infinities are about states. If you are going to divide by infinity you have to specify WHICH infinity.