Answer:
the unit rate of 1/7 is itself (1/7), and for 1/21 is 1/21.
Explanation:
this is because these rates/ratios are unit fractions. so if the numerater is 1, theres nothing you can do to simplify it.
you can check with the ceaser method as well, but you're still going to find the same solution.
plus, for example, if it takes 7 grams of sugar to make 1 cake, it wouldnt make sense for 1 gram of sugar to make 7 cakes.
hope this helped clear up your confusion <3