This is perhaps the most odd math question I have ever come across. Anyhow -
#1 - Positive, because smoking increases the chance of having lung cancer. (though technically there is not a linear relationship between the two as people do in fact receive lung cancer even when having not smoked)
#2 - No relationship. (Though one could argue a student may text more when given more free time as a consequence of having spent less time at school, but this is wholly subjective and unable to be substantiated by logic.)
#3 - Negative, due to the mass of the tootsie pop decreasing with each lick.
Of course, I am assuming when you say "positive" and "negative" you are speaking in terms of numbers or addition and subtraction rather than "positive" or "negative" socially.