The daughter should pick envelope 1. Unfortunately she picked envelope 3. Statements 1 and 2 were false, and the only true statement was statement 3. If the check was in envelope 1, that would make statement 1 false, statement 2 false and statement 3 is the only true statement. If the check was in envelope 2, statements 1 and 2 would both be true. If the check was in envelope 3, statements 1 and 3 would both be true.
Inless some one can tell me a way that 2 prisoners, at some point, don't out number the guards whether they are just dropping off and still in the boat or actually on land (because even if they are just dropping off and remain in the boat they are still on the other side of the river) I conclude this to be impossible. Please let me know an alternative if you figure one out because i'm stumped.
Riddles needing much effort or skill to accomplish, deal with, or understand. These won't tease your brain they will destroy it!