Now we’re going to talk about ~~tweetle beetles~~ how the
computer thinks. For example, what will the following block of code
output? Try to figure it out without running the code in Thonny.

```
x = 4 + 2 * 7
y = x / 2 - 3
z = (x + y) * 2
print(z)
```

If the answer is obvious to you, then you can probably skip this
section. Otherwise, I hope you enjoy my explanation of
**expressions**.

An expression is a piece of code that can be simplified to a single
value. On the first line, `4 + 2 * 7`

is an expression. It simplifies
to `18`

. But in programming, we say the expression **evaluates** to `18`

.

Technically, `42`

is also an expression—it evaluates to `42`

. After
the first line, `x`

is an expression that evaluates to `18`

.

When the computer sees `x = 4 + 2 * 7`

, it evaluates the expression
the same way a human would:

x = 4 + 2 * 7 -> x = 4 + 14 -> x = 18

Then the next line gets evaluated like this:

y = x / 2 - 3 -> y = 18 / 2 - 3 -> y = 9 - 3 -> y = 6

And finally we have:

z = (x + y) * 2 -> z = (18 + 6) * 2 -> z = 24 * 2 -> z = 48

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