SOLUTION: I am a parent trying to help a 7th grader: how can I explain: r-7 = 13 Thanks DAwn

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Question 25262: I am a parent trying to help a 7th grader: how can I explain:
r-7 = 13
Thanks
DAwn
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Try this:
The object is to get the variable r by itself. In your equation however, r has a 7 subtracted from it, so you need to "undo" this subtraction of 7 by adding (that's the opposite of subtracting) 7. But don't forget that whatever you do to one side of the equation, you must do exactly the same to the other side. So you must add 7 to the other side as well.
r+-+7+=+13 Add 7 to both sides of the equation.
r+-+7+%2B+7+=+13+%2B+7 Simplify this.
r+=+20 This is the answer!