The slope is the ratio between the change in the y and x values. When you write a line as
, the slope is the coefficient
. So, the slope of the first graph is 405, which means that the first plane flies with a speed of 405 miles per hour.
Similarly, from the table we can see that each time you increase x by 1, the distance traveled increases by 435. So, the slope of the second graph is 435, which means that the second plane flies with a speed of 435 miles per hour, and is thus faster.