If it is directly proportional, then:
m = kx
10 = k x -4
k = -2.5
m = 3 x -2.5
m= 7.5
Hope I helped!
T=volume÷rate
this will cancel out gal and leave min
22000 gal ÷ 400 gal/min
55 min
Luke: 2 miles in 40 minutes, 20 minutes a mile, (2/40 = 20 minutes a mile)
Luke's speed is 3 miles an hour (60minutes/20minutes a mile = 3miles).
Sally: 0.05 miles a minute, 60 minutes in an hour, 60 x 0.05 = 3 miles an hour. Or 0.05 miles a minute, 40 minutes walked, 40 x 0.05 = 2 miles walked.
There are a few other ways to show that they are accurate rates.
So yes, they are both correct rates.