Answer:
[tex]4+c=2\frac{1}{4}+2\frac{1}{3},\\\\\frac{7}{12}\:\text{more cups of flour}[/tex]
Step-by-step explanation:
The total amount of flour, in cups, Matthew needs is equal to [tex]2\frac{1}{4}+2\frac{1}{3}=4\frac{7}{12}[/tex]. Because he only has 4 cups, we can write the following expression to determine how many additional cups of flour he needs:
[tex]4+c=2\frac{1}{4}+2\frac{1}{3},\\\\4+c=\frac{7}{12}, \\\\c=\boxed{\frac{7}{12}\:\text{more cups of flour}}[/tex]