Answer choice B.
3 min/mile = 20 MPH
Total Travel time is 48 minutes 48 minutes / 60 minutes per hour = 4/5 of an hour
4/5 hours * 20 MPH = 16 miles, the maximum distance that can be traveled.
Cyclist starts 10 miles from home, wants to continuing riding then turn back and return home.
We can understand the additonal distance ridden as X. Distance from home before turning around will be 10 + x.
His trip return will be X + 10 + X = 16 | 2x + 10 = 16 | 2x = 6 | x =3 additional miles
Alternatively,
3 minutes / mile = 1/3 miles Miles Per Minute (MPM)
1/3 MPM * 48 minutes = 16 miles can be traveled
Must ride at least 10 miles back home
6 miles is left to be traveld, away from and back to starting point | 10 --> X & X --> 10 | 2x = 6 | x = 3
Sorry for any spelling mistakes... I suck at spelling. Thankfully that's not on the GMAT Focus

Bunuel
At 10:00 p.m., a cyclist is 10 miles from home on a straight road. From that time on, the cyclist continues riding farther from home at a constant speed of 3 minutes per mile, then turns around and rides back toward home at the same speed along the same road. If the cyclist must arrive back home at 10:48 p.m., how many additional miles can the cyclist travel away from home after 10:00 p.m. before turning around?
A. 2
B. 3
C. 6
D. 9
E. 12