Q.Write the set $A = \{2, 4, 6, 8, 10\}$ in set-builder form.

Roster form lists the elements directly; to convert to set-builder form, spot the common property every listed element shares.

The elements $2, 4, 6, 8, 10$ are exactly the even natural numbers less than 11.

Step 1 — List and study the given elements. $A = \{2, 4, 6, 8, 10\}$. All five elements are even, and they are natural numbers.

Step 2 — Find the upper bound. The largest element is 10, and the next even number, 12, is not included — so the defining condition should stop just after 10; "$x < 11$" captures exactly $2, 4, 6, 8, 10$ among the even natural numbers (the next even number 12 is excluded, and choosing $x < 11$ rather than $x \le 10$ is simply a stylistic choice — both work).

Step 3 — Write the rule. $x$ must be a natural number, even, and less than 11.