This is less of an issue with the Challenges and more of a suggestion. I think it would be a little more helpful for this level if you guys switched Challenges 2 & 3.
Challenge 3 is a nice simple If/Else conditional loop like what was covered in the instructional video.
Challenge 2 is a more complicated If/Else loop (that really only uses the If portion) in a While loop that requires users to remember the little used modulus symbol.
While I was doing the challenges, I sweated my way through Challenge 2 and eventually had to look for help to find out about the modulus symbol and that I didn't need to put anything for the Else condition. For Challenge 3 I actually went straight to the help area because I couldn't believe that the answer could really be that simple after Challenge 2; image my chagrin when I realize that it was.
I think switching Challenge 2 with Challenge 3 would be better for your students because it will give them a chance to practice the basic If/Else conditional loop before throwing shenanigans like modulus symbols and empty Else conditions at them.
edit (from moderator): Bijan had liked this, too, but the like was lost when I moved this. Sorry!