What prerequisite skills are needed for students to begin using Hands-On Equations?

It would be helpful if students can perform basic computations, such as counting by 7’s, adding 9 and 8 mentally, etc.  Knowledge of multiplication is not needed. However, some teachers have used Hands-On Equations with students having weak computation skills, and they allowed their students to use a calculator to perform the calculations. Other teachers have found that the program served to motivate their students to want to learn those skills.