1. -1 is the input value that produces the same output value in both charts.
2. Step 3 has an incorrect instruction.
Answer:
1 and a 1/2 hours
Basic explanation:
1125/750 equals 1.5. This means that the duration of the flight is 1.5 hrs.
The slope of an horizontal line is always zero.
This comes from the fact that the slope is given by:

and if two points lie on a horizontal line this means that their y components are equals and then the numerator is zero.
Therefore the slope is zero.