#### Answer

$\frac{51}{4}$

#### Work Step by Step

To write $12\frac{3}{4}$ as a mixed number, we must multiply the whole number in front of the fraction and the denominator together.
$12\times4=48$
Next, take the sum of the number above and the numerator.
$48+3=51$
This will be the numerator of the mixed number. We will use the original denominator as the denominator of the mixed number. Therefore, $12\frac{3}{4}=\frac{51}{4}$.