Why does my child think 5x + 3 = 2x + 15 gives 7x?
Your child adds the x terms from both sides instead of subtracting one from the other.
Why children do it
With x on both sides, children know the x terms need to come together, and adding is the first thing they try. But to clear x from one side, the smaller x term is taken away from both sides: 5x − 2x leaves 3x, so 3x + 3 = 15.
How to help at home
To bring the x terms together, take the smaller one away from both sides, rather than adding them.
The right way
Solve: 5x + 3 = 2x + 15
- 3x + 3 = 15Subtract 2x from both sides.
- 3x = 12Subtract 3 from both sides.
- x = 4Divide both sides by 3.
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