Answer:
r=
![-(S)/(L) +1](https://img.qammunity.org/2022/formulas/mathematics/high-school/eh71ig9daxr6s0q9xvdpm534pmg76n8xk9.png)
Explanation:
You would want to isolate the r by itself by doing all the opposite operations.
First, you can divide the L to get
1-r =
![(S)/(L)](https://img.qammunity.org/2022/formulas/mathematics/high-school/j12inaloshzec1p67g5geggy5pmshnqevi.png)
Next, move the 1 to the other side to get
-r=
![(S)/(L) -1](https://img.qammunity.org/2022/formulas/mathematics/high-school/6gdftc7jsuh23ovwc5qr7jmwi9zh1djmj1.png)
Then, we would not want to keep the negative so, move it to the other side to get
r=
![-(S)/(L) +1](https://img.qammunity.org/2022/formulas/mathematics/high-school/eh71ig9daxr6s0q9xvdpm534pmg76n8xk9.png)
(Note the 1 changed to a positive because we move the negative to the other side so, negative or negative 1 will be positive.