Number of cups of sugar Ricky needs = [tex]3 \frac{1}{4} = \frac{13}{4} [/tex]
Number of cups of sugar Ricky already has = [tex]2 \frac{1}{2} = \frac{5}{2} [/tex]
Hence, number of cups of sugar Ricky requires = [tex] \frac{13}{4} - \frac{5}{2} = \frac{13 -10}{4} = \frac{3}{4} [/tex]