A line is represented by the following expression:

Since they are parallel because they have the same slope, we can find the distance between them with the formula for distance between points:

Distance between points is represented by the following expression:
![d=\sqrt[]{(x_2-x_1)^2+(y_2-y_1)}^2](https://img.qammunity.org/2023/formulas/mathematics/college/turln5c5kgv0mczyvn8l8gdnipok6l3p1t.png)
![\begin{gathered} d=\sqrt[]{(1-1)^2+(9-0)^2} \\ d=\sqrt[]{9^2} \\ d=9\text{ units} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/6uk2fcyd1fem6y3rkfaofrq7r7b1ey15vn.png)
The distance between the lines is 9 units.