Final answer:
The probability of Alan's character casting a spell in a role-playing game, given the odds of 13/6 in favor, is calculated as 13/19 when considering the total number of outcomes.
Step-by-step explanation:
The student provided the odds in favor of casting a spell as 13 to 6. This can be understood to mean that for every 6 instances where the spell is not cast, there are 13 instances where the spell is cast.
To find the probability of casting the spell, one must consider both the favorable outcomes (casting the spell) and the total outcomes (both casting and not casting the spell).
The total number of outcomes equals the sum of the odds in favor and the odds against, which is 13 (favorable) + 6 (unfavorable) = 19 (total). The probability, then, is the ratio of favorable outcomes to the total number of possible outcomes. Thus, the probability of casting a spell is 13/19.