Lesson video
Start here.
Press play for Monday’s lesson on keeping an equation balanced. Then catch the Bandit Error further down the page and finish with the Mission.
October · Week 1 · Day 1
One-Step Equations: Meet the Balance
An equation is a promise: both sides name the same number. Today is about why every move has to happen on both sides — and what breaks the moment one side changes without the other.
Three things to lock in.
These are the ideas the Mission asks you to use.
EquationA claim that two expressions name the same number. x + 5 = 12 is a claim you can check.
Inverse operationThe move that undoes another. + 5 is undone by − 5.
BalanceWhatever you do to one side you do to the other, on the same line.
✗ Today’s Bandit Error
Bandit fixes only one side.
He takes the 5 off the left and leaves the right exactly as it was.
✗ x + 5 − 5 = 12 → x = 12
✓ x + 5 − 5 = 12 − 5 → x = 7
Removing 5 from the left alone breaks the promise the equals sign makes. The move has to reach both sides, on the same line.
Free Mission
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Monday’s Mission has 10 problems plus the Mission Debrief so you can check your reasoning when you finish.
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