I give this substitution problem every year in my summer Algebra I refresher class. The mistake they almost all make, is a classic PEMDAS problem. So I teach order of operations rather strictly as illustrated in the example below. Here are 2 things essential things I teach them:
- Do only ONE level per line (M/D and A/S are the same level). Put the letter(s) you are doing next to each line.
- Do NOT drop parenthesis until the M/D line (i.e. leave them in the