Answer:
[tex]\frac56[/tex] cups
Step-by-step explanation:
The serving size is proportional to the amount of milk used, so we have
[tex]\frac{2/3}{4/5}=\frac x1[/tex]
where [tex]x[/tex] is the amount of milk needed for 1 serving. The right side is simply [tex]x[/tex]. We now simplify
[tex]x=\frac23\cdot\frac54=\frac{10}{12}=\frac56[/tex]
Therefore [tex]\frac56[/tex] cups of milk are needed for 1 serving.
