Premier's Reading Challenge Update

Well done to Jake, Nelson, Poppy and Sam on completing the Reading Challenge! IT was great to see you make use of some spare time on the holidays to complete this. Awesome work. We now have 12 students finished and some who are almost finished. How can we work out the number of people left to complete it? There's 23 children in our class so...
12 + ? = 23

Also, Millie has read 68 books! I have a feeling Ella is going for the 100 book Super Challenge as she has already logged 86 books!
Hmmmm, how many more books until 100....
For Millie..... 68 + ? = 100
For Ella...... 86 + ? = 100