What is the probability that we would get success in our one trail to guess the number ?

Question

A 3 digit number is such that 2 digits of the number are 1 and 2.
What is the probability that we would get success in our one trail to guess the number ?

Answer 1

Total success cases
[1-9]*[x][y] where x and y are 1 & 2 or reverse so total cases 9*2 = 18
[x][0-9][y] total cases 10*2=20
[x][y][0-9] total cases 10*2 = 20

Total fav cases = 58
Total possible cases [1-9][0-9][0-9] = 900

Probability 58/900