write the following solution in interval notation: z < 20

Explanation:

Step1: Understand interval notation rules

In interval notation, for an inequality like $z < a$, we use an open - interval on the side of $a$ (since $a$ is not included) and $-\infty$ on the other side with an open - interval as well (because $\infty$ is not a real number).

Step2: Write the interval

For $z < 20$, the interval notation is $(-\infty, 20)$.

Answer:

$(-\infty, 20)$