If someone swims within 30 minutes of eating, then they will get a cramp.
If someone gets a cramp, then they are likely to drown.
Thus, if someone swims within 30 minutes of eating, then they are likely to drown.
Answer: If you assume that the conditional and fact above are true, must the conclusion also be true?
Yes, the conclusion must be true if the conditional and fact are true.
No, the conclusion might be false even if the conditional and fact are true.