Week 1 was Variables & Expressions. Four lessons, four Bandit Errors, every one of them on camera. I am writing them down because a mistake you have looked at properly is a lot less likely to come back.

Here is the whole list. No editing.

Monday: 3x + 7 became 10x

Sunny put 3x + 7 on the board. I saw a 3 and a 7 and added them. Ten. Stick the x on the end. 10x.

The fix: 3x means 3 times x, three of the same mystery amount. The 7 is seven known units. They are different kinds of thing, so they do not join up. Without a value for x, 3x + 7 just stays 3x + 7.
3x + 7not 10x

Tuesday: I counted three terms in 4n + 9

Four, n, nine. Three pieces, three terms. I can count.

The fix: plus and minus separate terms. Multiplication does not. 4n is 4 times n, so it is one term, and 4n + 9 has two terms.
term 1: 4nterm 2: +9

Same lesson, I almost dropped a sign, too. In 6a − 2b + 5, the second term is −2b, so its coefficient is −2, not 2. The sign travels with the term that follows it.

Wednesday: “five less than x” became 5 − x

Five came first in the sentence, so five went first in the math. Three seconds flat. Very proud. Backwards.

The fix: “less than” flips the order. Start with x, then take 5 away. Check with x = 12: five less than 12 is 7, and 12 − 5 = 7. The other way gives 5 − 12 = −7.
x − 5not 5 − x

Thursday: x = 4 turned 3x + 7 into 3 + 4 + 7

I put the 4 in where the x was, which was right. Then I added everything and got 14, which was not.

The fix: replace the variable, keep the operation. 3x becomes 3(4), not 3 + 4.
3(4) + 712 + 7= 19

If that one looks familiar, it should. It is Monday’s mistake in a disguise. Same hidden times sign, same plus sneaking in. I did not spot that until I wrote this list, which is kind of the whole reason for the list.

Bandit note: Four errors, but really three ideas. The hidden times sign got me twice in one week.

The one I still have to think about

Honestly? “Less than.” The other three I can feel now. 3x looks like multiplying to me, and 4n looks like one piece. But when a phrase says “less than” or “fewer than,” I still have to stop and flip it on purpose. My first instinct still wants sentence order.

So on that one, I do not trust my first instinct. I ask what I am starting with, and I plug in a number to check. It is not automatic yet. That is fine. It is on the list, so I know exactly where to look.

The notebook version: Monday, 3x is not 3 + x. Tuesday, plus and minus split terms; multiplication does not. Wednesday, “less than” flips the order. Thursday, replace the variable, keep the operation. Still working on: Wednesday.