Question

Which values from the specified set make up the solution set of the inequality?

Answer 1

You may solve this problem in two ways:

If you solve the inequality explicitly (divide both sides by 4), you get

$\dfrac{4n}{4} < \dfrac{16}{4} \iff n < 4$

So, if $n$ has to be stricktly less than 4, you can only choose 1, 2 and 3 as answers.

Alternatively, you can plug in all of the values you're proposed and check if the inequality holds:

If $n=1$, you have $4$, which is true.

If $n=2$, you have $8$, which is true.

If $n=3$, you have $12$, which is true.

If $n=4$, you have $16$, which is false.

So, again, only 1, 2 and 3 are solutions.