Line 1. Vertical. Undefined slope.
Line 2. -4/3
Line 3. 4/3
Line 4. Vertical. Undefined slope.
Line 5. 7/3
Line 6. -7/3
Line 7. Horizontal line. Slope 0
Line 8. Horizontal line. Slope 0
Line 9. Vertical line. Undefined slope.
Line 10. Vertical line. Undefined slope.
Line 11. Horizontal line. Slope 0
Line 12. Vertical line. Undefined slope.
These slopes can be found using the rise and run method. All vertical lines are undefined and all horizontal lines are 0.