Hello there.
Alexis has 36 marbles he gives 1/9 of marbles away to Sara. How many marbles did Sara have?
Answer: Just simply divide 36 by the denominator.
36/9 = 4.
If the numerator was above one then you would have had to multiply by that.
However, in this case it is not required to do so.
In short, Your answer is Sara has 4 marbles.
Hope This Helps You!
Good Luck Studying ^-^