In order to find the slopes, you take into accoun the following formula for the slope of a line:
m = (y2 - y1)/(x2 - x1)
where (x1,y1) and (x2,y2) are two points of the line.
In the first case, for Fast Freddy, you can notice in the graph, that two points of the line can be:
(x1,y1) => (0,0)
(x2,y2) => (8,2)
You replace the previoues values of the coordinates in the formula for m:
m = (2 - 0)/(8 - 2) = 2/8 = 1/4 = 0.25
In this type of graph the slope of the line means the speed of motion.
Hence, the speed of Fast Freddy is 0.25 mi/min
In the second case, for Speedy Sam, you can use the values of the table to replace in the formula for m. You can use, from the table, the following points:
(x1,y1) => (4, 1/2)
(x2,y2) => (32, 4)
m = (4 - 1/2)/(32 - 4) = (7/2)/(28) = 1/8 = 0.125
Hence, the speed of Speedy Sam is 0.125 mi/min
Finally, you can conclude that Fast Freddy is faster than Speedy Sam.