$3\frac{1}{4}$ = 3 + $\frac{1}{4}$ = $\frac{3\times 4}{1\times 4}$ + $\frac{1}{4}$ = $\frac{12 + 1}{4}$ = $\frac{13}{4}$
$3\frac{1}{4}$ = 3 + $\frac{1}{4}$ = $\frac{3\times 4}{1\times 4}$ + $\frac{1}{4}$ = $\frac{12 + 1}{4}$ = $\frac{13}{4}$