9n-10=71
9n+10=+10
9n=81
9n/9=81/9
n=9

This is correct

It is exactly correct

Although you got the answer, I don't suggest you put it as you put it. Because the way you put it is confusing.


]9n-10=71
9n+10=+10
9n=81
9n/9=81/9
n=9

Where does the bold part come from?

You have to show this:

9n - 10 +10 = 71 + 10

and not directly add 10, because the other side is not only '10'.

You are correct

The check is:

9(9)-10 = 71; which is true, so you got the right answer.

I'm in agreement that it was confusing getting there.