This identity relates the inradius \( r \), the exradii \( r_1, r_2, r_3 \), and the triangle's side lengths.
From known triangle geometry identities:
\[
s \left( \frac{r_1 - r}{a} + \frac{r_2 - r}{b} + \frac{r_3 - r}{c} \right) = r_1 + r_2 + r_3 - 3r
\]
But it turns out the original expression actually simplifies as:
\[
s \left( \frac{r_1 - r}{a} + \frac{r_2 - r}{b} + \frac{r_3 - r}{c} \right) = r_1 + r_2 + r_3
\]