1.
Well ok x / 0 doesn't actually necessarily equal infinity.
If you look at the graph of 1 / x, where x is a variable, it creates a hyperbola, which never actually reaches zero, but when it does it reaches both infinity and negative infinity in two points.
So it gets a bit trippy, but some people just call it infinity to get rid of the trippyness
Here's a question
f(x) = (x^2 - 9) / (x - 3)
What happens to f(x) as x approaches 3?