SOLUTION: I am trying to figure out what is wrong with this answer and how do I correct it... 3(a+7)=3a+7

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Question 795731: I am trying to figure out what is wrong with this answer and how do I correct it... 3(a+7)=3a+7
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
3%28a%2B7%29=3a%2B7
3a%2B3%2A7=3a%2B7
3a-3a%2B21=3a-3a%2B7
21=7, FALSE.

The left side and the right side are not equal. Applying the distributive property to the left side gives you "3a" and the right side is expressed with "3a" also. No other "a" terms are in the equation. An attempt to isolate terms of "a" onto only one side of the equation applies the additive inverse property and you lose "a". The final result is a false statement.