Answer:
[tex]x=\frac{13+y}{5}[/tex]
Step-by-step explanation:
Grandma Gertrude gives 13 and Fien gives y.
[tex]x=13+y[/tex]
The total amount of jewelry divided evenly between the 5 sisters:
[tex]x=\frac{13+y}{5}[/tex]
Nothing further can be done without knowing another value.