Could someone please explain how to solve this?

What is the slope of the line that contains the points (4,8) and (9,8)? what type of line is it?

The speed of a falling object increases at a constant rate as time increases since the object was dropped. which graph could represent the relationship betweent time in seconds, and s, speed in meters per second? speed of a falling object object over time

If 3x+8=3x+8 is it one solution or no solution