First, let's get the unit rate.
1.5 hours for 915 miles, so
[tex]\frac{1.5 hours}{915 miles} = \frac{1 hour}{x.miles}[/tex]
Cross multiplying gives us 1.5x = 915, divide by 1.5, and we get 610 miles. This is the answer for the top left. This means the plane was going 610 mph.
The speed will be constant because it tells us this.
Then, we multiply 610 by the time to fill in the rest of the distances.
For t, we can figure out the distance is 610 times t, as you can see I have written down.
See attached file below.
I hope this helps, have a nice day! :D