Yes you can, There are many simple ways of displaying this. An easy example is to take any odd integer number and divide it by two. This will always give an answer ending in .5For example:7/2 = 3.5...
Because if you are wrong, people can still have a look at your working, and improve or correct you. Particularly useful for exams, where you may be awarded some marks even if you get the wrong answer.
There are some math problmes that do require virtualization but it is also hard to find a place to do the problem on. There are teachers who have been educated in this particular subject.
Either define finite first (usually as equivalent to a set of the form {1,2,3,...,n} for an integer n, in which case infinite is not finite; or use a set is infinite if and only if it is equivalent...