Hi there! Hopefully this helps!
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Answer: r = 7.
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[tex]17 = r + 10[/tex]
Swap sides so that all variable terms are on the left hand side.
[tex]r + 10 = 17[/tex]
Subtract 10 from both sides.
[tex]r = 17 - 10[/tex]
Subtract 10 from 17 to get, you guessed it, 7!
