Answer
If concentration is on the Y-axis and Time is on the X-axis (time always goes on the X-axis), then the rate is the slope. Slope = Rise/Run (distance on Y-axis/distance on X-axis)
Work Step by Step
If concentration is on the Y-axis and Time is on the X-axis (time always goes on the X-axis), then the rate is the slope. Slope = Rise/Run (distance on Y-axis/distance on X-axis)