On his trip from Alba to Benton, Julio drove the first x miles at an average rate of 50 miles per hour and the remaining distance at an average rate of 60 miles per hour. How long did it take Julio to drive the first x miles?

1) On this trip, Julio drove for a total of 10 hours and drove a total of 530 miles.

2) On this trip, it took Julio 4 more hours to drive the first x miles than to drive the remaining distance.

From the statement :

If the total distance is D.

(x/50) + + (D-x)/60 = Total Time

Now from (1), (x/50) + + (D-x)/60 =10

and D = 530

From the above two equation x can be calculated and so x/50. Hence sufficient

From (2), x/50 + 4 = (D-x)/50

One equation and two unknown ,Hence impossible to find out x. ( Not sufficient)

Therefore answer in (A).

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