Answer:
1/15
Explanation:
Ok, so let's look at it this way.
So there are 5 possible letters. This means you have a 1/5 chance of getting to I.
Next, if you count up all the numbers, we can see there are 15 options and 5 3's so you have 5/15, which can be simplified to 1/3. But because this is a compound problem, you need to multiply 1/5 and 1/3 together to get 1/15. :)