3/4 is my answer, and I came here to check if it was correct...
If it helps (text version):
The digits 2,3,5, and 7 are arranged randomly to form a four-digit number. What is the probability that the number is odd? Express your answer as a common fraction.
The number of possible arrangements of the digits is 4! = 24
Let's look at those which form even numbers.....this occurs when the "2" appears at the end of a number
So....in that case.....the other digits can be arranged in 3! = 6 ways
So.....there are 6 even numbers and 18 odd
18 / 24 = 3 / 4 and you are correct!!!!