The unit rate that Jeremy can row is 1.33 miles per hour.
Unit rate is defined as the distance over a time period. The distance that Jeremy can row is given and the time period is given.
The distance (miles) = 1/3 = 0.33
The time period (hours) = 1/4 = 0.25
The unit rate is distance per time:
= 0.33/0.25 = 1.33
The unit rate that Jeremy can row is 1.33 miles per hour.