The probability of flipping a five is ⅙, so the probability of not flipping a five is ⅚.
The probability of no fives at all is (⅚)¹².
The probability of only one five is 12(⅚)¹¹(⅙) because the single five can come first, second, third, etc., but nowhere else.
So the probability of less than 2 fives is the sum of no-fives and one-five:
(⅚)¹²+12(⅚)¹¹(⅙)=(⅚)¹¹(⅚+2)=0.3813 or about 38.13%.