So the 9 tells us it will be a multiple of 9 and the (a - b) tells us which multiple of 9. This means that the difference between the two two-digit numbers is 9 times the difference between the two digits!
At the end of the day, Michael and Liz thanked all participants for their commitment to the project as a whole. We looked forward to the conference on October 13, which will celebrate the project's achievements and begin to unpick some ideas associated with mastering mathematics in the context of problem solving.
First published February 2014, last updated July 2015