No, neither equation is currently written in a form where \( r \) or \( b \) is isolated (i.e., written as \( r = \) some value or \( b = \) some value). To use substitution, you will need to rearrange one of the equations to express one variable in terms of the other.
For example, from the second equation, you can express \( b \) in terms of \( r \):
\[ b = 10 - r \]
Once you have that, you can substitute this expression for \( b \) into the first equation. Alternatively, you could isolate \( r \) in the same way.