Explain equation-solving steps as logical consequences of equality and justify solution methods.
Find the first invalid solving step
Problem
Find the first invalid step in this proposed solution: \(3(x~+~2)~=~15,~3x~+~2~=~15,~3x~=~13,~x~=~13/3\).
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What this problem is really about
An error audit must move in chronological order, because later work may be consistent with an already broken equation. We’ll compare each line with the one immediately before it, beginning by expanding the grouped expression with the outside factor applied to every term. The first transition that changes the expression’s value is the first invalid step, regardless of what follows.
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