List all the elements of the following sers :

$D = \{ x:x$ is a letter in the word $"\mathrm{LOYAL}" $ $\} $

What universal set $(s)$ would you propose for each of the following :

The set of right triangles

Let $A, B,$ and $C$ be the sets such that $A \cup B=A \cup C$ and $A \cap B=A \cap C$. Show that $B = C$

Which of the following are examples of the null set

Set of even prime numbers

List all the elements of the following sers :

$B = \{ x:x$ is an integer $; - \frac{1}{2} < n < \frac{9}{2}\} $

Which of the following are sets ? Justify your answer.

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