Answer: It would take 1 hour and 30 minutes for one people do it.
If 5 people do it would take less time. If there are 5 people delivering the letters it would take them 12 minutes ti deliver all 1,000 letters.
If you round 75 to the nearest tenth it would be 80
Df = g - 10
To solve for d, divide both sides by f.
df / f = (g - 10) / f
d = (g - 10) / f
I hope this explains it.