Answer:
1:7
Step-by-step explanation:
The number of possible outcomes is 2*2*2 = 8
The number of ways of getting 3 tails is 1
The odds against - the ratio of the number of ways that an outcome cannot occur compared to in how many ways it can occur.
ways it can occur -1
ways it cannot occur - 8-1 = 7
1:7
