SOLUTION:
3 cups = 9 cupcakes
x cups = 1 cupcake
Cross-multiplication:
[tex]\begin{gathered} 9x\text{ = 3} \\ \text{Dividing both sides by 9} \\ \frac{9x}{9}\text{ = }\frac{3}{9} \\ \\ x\text{ = }\frac{1}{3} \end{gathered}[/tex]CONCLUSION:
One-third of a cup of flour is needed to make one cup of cake.