What's $P(z < −1.51\ {\rm or}\ z > 2.50)$ when $z$ is normally distributed?

Question

Let $z$ denote a random variable having a normal distribution with $\mu = 0$ and $\sigma = 1$. Determine the following probability. (Round all answers to four decimal places.)

$$P(z < −1.51\ {\rm or}\ z > 2.50)$$

How does one approach this? I am unaware of what the OR means. I assumed it was a + but it appears to be the wrong answer.

Answer 1

Hint: Maybe this figure will help: