P(roll a total of 2 or 12 on a pair of fair 6-sided die, numbered 1 through 6)
# ways you want / # ways anything can happen
Only 1 way to roll a 2 (roll 1,1).
Only 1 way to roll a 12 (roll 6,6).
# ways to roll (2 or 12) = 2
# ways to roll anything: 6 * 6 = 36
P(roll 2 or 12) = 2 / 36 = 1 / 18 = about 0.05555