Given Data:
The number of cups of oatmeal is 5.
Stella have 1/3 cups everday.
Let the number of days be x. Then the number of days can be calculated as,
[tex]\begin{gathered} 5=x\times\frac{1}{3} \\ 5\times3=x \\ 15=x \end{gathered}[/tex]Thus, the number of days is 15.