E is for exponents and the laws already mentioned.
By doing this students felt they didn't do better when using only numbers but eliminated many mistakes in the algebra portion of their math. So by Negation, the subtraction is replaced by a plus and the 3 becomes negative. For many students this seemed to eliminate most of this type of error. Divsioin, Multiplication from left to right Addition, Subtraction from left to right Most of the students I work with are adults who are returning to school to complete junior and senior high scholl to go onto tecchnical institutes or to gain a high school diploma. Other students I deal with are Learning Disabled and we work together to develop strategies to help them learn more effectively.