Challenge scrolls are logical problems posed to the player by an NPC. Challenge scrolls appear in level 2 and level 3 clues in Treasure Trails. Challenge scrolls are 'step two' of a clue: first the player has to find the right NPC to speak to (when they get a cryptic or anagram clue), and then they have to solve the riddle, to advance along their trail. Play RuneScape with sufficient RuneScape Gold is a wise choice to make.
So, challenge scrolls don't count as a regular clue. To complete the scroll, view the question on the scroll, then speak to the NPC which gave it to provide the answer. When the correct answer is provided the challenge is complete, and the player will receive either the next clue, or the reward.
It is also possible able to obtain more than one challenge scroll by asking the NPC you got it from with a full inventory. Every time you talk to the NPC another appears on the ground that you can pick up.