The ratio of cups to ounces is:
[tex]\frac{1\text{ cup}}{8\text{ ounces}}[/tex]Then, let's establish the proportion:
[tex]\frac{1\text{ cup}}{8\text{ ounces}}=\frac{x}{28\text{ ounces}}[/tex]And solve for x:
[tex]\begin{gathered} x=\frac{1\times28}{8} \\ x=3.5\text{ cups} \end{gathered}[/tex]Then, Jhon will get 3.5 cups from the bottle