Use the following formula for the distance traveled:
distance = speed x time
speed = 23 mi/h
time = 31 min
convert the time to hours:
31 min · (1 hour/60 min) = 0.516 hour
next, replace speed and time in the formula for the distance:
distance = (23 mi/h) x (0.516 h)
distance = 11.88 mi
Hence, Bob rides 11.88 miles in 23 minutes