ANSWER
1/6
EXPLANATION
If we have a fair die and we toss it only once, then the probability of getting any of the numbers is the same,
[tex]P(one.number)=\frac{\#favorable.outcomes}{\#total.outcomes}[/tex]The die has 6 faces, so the total number of outcomes is 6 and the number of favorable outcomes is always 1, since the numbers on the die don't repeat,
[tex]P(six)=\frac{1}{6}[/tex]Hence, the probability of rolling a 6 is 1/6.