# Undoing the steps/backtracking

I’ve seen this approach in both CME and also in the Discovering Algebra series. I like it as a concrete model for introducing solving equations. It also meshes well with using number tricks to approach algebraic expressions (which both of these curricula do as well).

Here are some resources for introducing solving equations via backtracking/undoing the steps:

Reminder: Things get awkward when you try to backtrack from expressions such as $5 - x$. For these, there’s no getting around observing that $5-x = 5 + (-x) = -x + 5$, but that needs to be done explicitly.