Why does my child solve x + 5 = 12 as x = 17?
Your child adds to undo an addition, instead of subtracting.
Why children do it
Undoing adding 5 means taking 5 away, from both sides. Children who copy the sign they can see add 5 again, which moves x further from being on its own. x + 5 = 12 means x is 5 less than 12, so x = 7.
How to help at home
Ask what undoes adding a number. Taking it away does, so the same number is taken from both sides.
The right way
Solve: 3x + 5 = 20
- 3x = 15Subtract 5 from both sides.
- x = 5Divide both sides by 3.
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