Answer:
The slope of a position-time graph represents an object’s velocity.
Explanation:
In a position-time graph, the values on the x-axis represent the time, while the values on the y-axis represent the position of the object.
Velocity is defined as the ratio between the displacement of an object and the time taken:

However, we can see that this definition corresponds to the slope of the curve in a position-time graph. In fact:
, the displacement, corresponds to the difference in position, so the difference between the values on the y-axis: 
, the time interval, corresponds to the difference in times, so the difference between the values on the x-axis: 
So, the velocity is

which corresponds to the slope of the curve.