Question 1376
Let V be the speed of his going to the fair, then his speed of the return trip
 was 2V.
 Now the total distance of the round trip is 2*4 = 8 miles.

 By Speed = Distance / Time , and so  Time =  Distance /SPeed,
 we have 3 = 8/V + 8/(2V),
 Cancel the denominator by multiple by 2, 6V = 16 + 8 = 24.
 so, V =4 and 2V = 8.

 Hence, his speed going to the fair was 4 miles/hr,and 
 his speed backing home was 8 miles/hr.