Asked by Sara

Did I do this right? Just want to make sure.

15 = r-1
+ 6 +6

r = 21

Answers

Ms. Sue
You need to get the unknown on one side of the equation and the known on the other side.

15 = r-1

Add 1 to both sides of the equation.

15 + 1 = r -1 + 1
16 = r

Here's how we can prove it.
Substitute 16 for r.

15 = 16 - 1

Yep. We have the right answer.

Sara
Thank you Ms. Sue for the explanation. I'm sorry, I accidentally wrote -1 instead of -6. It was supposed to be 15 = r-6.
Ms. Sue
Your original answer of 21 is correct. :-)

Sara
thank you, and sorry once again for my mistake.
Ms. Sue
You're very welcome.

We're all human and make typos and other mistakes. :-)