Let x be the amount of sugar, in cups needed to make \(2\frac{1}{2}\) dozen or 30 cupcakes. Using the ratio sugar/cupcake, we write the proportion:

\(x/30=1/3/6\)

Solve for x:

\(x/30=1/18\)

Multiply both sides by 30:

\((x/30)(30)=(1/18)(30)\)

\(x=5/3=1(2/3)\) cups

So, the answer is choice A.

\(x/30=1/3/6\)

Solve for x:

\(x/30=1/18\)

Multiply both sides by 30:

\((x/30)(30)=(1/18)(30)\)

\(x=5/3=1(2/3)\) cups

So, the answer is choice A.