Andrew swims 5/12 of a lap in 1/4 of a minute. And we need to find the rate he swims in laps per minute.
So, we have the following proportion:
number of laps number of minutes
5/12 1/4
x 1
Now, we can solve for x (the rate of laps per minute) by cross multiplying the above values. We obtain:

Now, we can isolate x on the left side to find its value by multiplying both sides of the above equation by 4. We obtain:

Therefore, Andrew's unit rate for swimming is:
