Taking the set of natural numbers as the universal set,write down the complement of the following set:
$A = \{ x: x \ge 7 \}$

(N/A) Let the universal set be $U = N$,where $N$ is the set of all natural numbers.
The given set is $A = \{ x: x \in N \text{ and } x \ge 7 \}$.
The complement of set $A$,denoted by $A^\prime$,is defined as $A^\prime = \{ x: x \in U \text{ and } x \notin A \}$.
Since $A$ contains all natural numbers greater than or equal to $7$,its complement $A^\prime$ will contain all natural numbers less than $7$.
Therefore,$A^\prime = \{ x: x \in N \text{ and } x < 7 \}$.