To solve for r, we first have to get it by itself. Here is how you do it:
9r+2=38
First subtract 2 from each side so that all we have left to do is isolate r.
9r+2-2=38-2
9r=36
Then to get r by itself, we have to do the opposite of multiply and that is divide by 9.
9r =36
9 9
r=4
r=4 is your final answer. To check it, plug it into the equation, 9(4)+2=38.