The method from rung 2 is sound — the trouble is people apply it in the wrong order or lose track of a sign. Both are fixable habits, not talent problems.
Trap One: the Order
It's tempting to divide first when you see 2x + 3 = 11 — but that's wrong, because the + 3 wasn't multiplied by 2, it was added on afterwards. You must undo the +/− before the ×/÷ (reverse BODMAS). Strip the + 3 away to get 2x = 8 first, then divide. In the toy, picking "÷ 2 first" will stop you and explain why.
Trap Two: the Negatives
Two sign-traps hide in here. First, to undo a subtraction you add — so 2x − 3 = 7 needs + 3 on both sides, not another subtract. Second, if the number multiplying x is negative — say −2x = 8 — dividing by −2 flips the sign of the answer: x = −4. The toy throws negatives at you on purpose and flags when the sign flips.
The Safety Check
If you're ever unsure, do the same move to both sides and ask "did I do the opposite operation?" Subtraction undoes addition; division undoes multiplication; and a negative divided by a negative is positive. Slow down on the sign and the order, and these two traps simply stop happening.