Discovery 15.1.
Read and briefly discuss the rules in your group. In particular, make sure everyone in your group understands the differences between the LHS and RHS in each of Rule A 2, Rule A 3, Rule S 2, Rule S 3, and Rule S 5.
It may help to come up with expressions for these algebra rules in plain English rather than letters and variables. For example, Rule A 2 states that order doesn’t matter in adding objects.