Explain why each step works
A worked solution can show what to do without revealing why the steps are valid. Adding a short reason beside each important step turns the sequence into an explanation. In an equation, subtracting the same amount from both sides preserves equality; naming that reason makes the action understandable.
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Add the missing justification
A learner can copy a correct calculation while remaining unsure why each operation was chosen. The written steps show the route, but not the reasoning that makes the route legitimate.
Self-explanation adds a reason to the action. Beside a step, ask why it is allowed, what it achieves or how it connects with the previous line.
For an equation, subtracting three from both sides is not merely the next move. It keeps the sides equal while removing a term from one side.
The explanation can be brief. One useful sentence is better than a paragraph that restates the calculation. If no reason comes to mind, that identifies a precise gap to investigate rather than leaving the whole solution vaguely confusing.