Three miles at 6 miles per hour is 3/6=1/2 hours.
Then, 3 miles at 3 miles per hour is 3/3=<<3/3=1>>1 hour.
The last 4 miles at 8 miles per hour is 4/8=1/2 hour.
In total, it took them 1/2 + 1 + 1/2 = <<1/2+1+1/2=2>>2 hours to push the car back to town.
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