The probability of getting the correct answer is 2/5. This means there are 2 events of getting it right out of 5 events total. Since there are 2 events of getting it right, there are 5-2 = 3 events of getting it wrong.
The odds against getting the right answer is 3:2. We list the number of ways to get it wrong first, a colon, then the number of ways of getting it right.
