A sea lion swims 23 miles in 1/5 hours.
We can calculate the unit rate of the swimming speed dividing the number of miles he swims in a certain period of time, by the hours of this period of time.
We can calculate this as:
[tex]v=\frac{23\text{ miles}}{\frac{1}{5}\text{hours}}=23\cdot\frac{5}{1}=115\text{ miles per hour}[/tex]We could have also calculated that if, in 1/5 of an hour, he travels 23 miles, in one hour (equal to 5/5) he would swim 23*5=115 miles.
At this rate it will take him 15/23 hours (approximately 0.65 hours) to swim 75 miles:
[tex]t=\frac{x}{v}=\frac{75\text{ miles}}{115\text{ miles/hour}}=\frac{15}{23}\text{hours}[/tex]