The fractions 2/18 and 1/9 are equivalent because the prior reduces to the latter. The first answer is correct, as instead of the four occurrences of the number two, Juan used the number two. The correct fraction should have been 4/18. The number of occurrences over the number of times the dice was rolled, not 2/18, the quantity over the number of rolls.
Hope this simplifies it,
Ahawk
