#### Answer

$5$

#### Work Step by Step

Let the unknown number here be $x$.
Four times a certain number is $4x$.
3 added to four times a certain number means $4x+3$.
Therefore, if 3 is added to four times a certain number, the result is 23 means that:
$4x+3=23$
Solving the above equation, we obtain:
$4x+3=23$
$4x=23-3$
$4x=20$
$x=\frac{20}{4}$
$x=5$
Therefore, the unknown number is $5$.