If $x = 4$ $(mod 7)$, then positive values of $x$ are

Given,

$x = 4$ $(mod 7)$, 

Here, we have, $4mod7$

As we know that a mod b is the reminder from the division of $a$ by $b$,

If $b>a>0$, then a mod $b=a$

So,

$4mod7=4$

Here, if add $7$ in $4$ we get $11$, again adding $7$ we get $18$.

Thus, the possible value of $x$ are $\left\{4,11,18,\dots \right\}$