In the previous chapter, you have learned to compose simple expressions in computer programming language.

In this chapter, you are going to learn how to compose nested expressions.

# Nested Expressions

Nested expressions are like russian dolls: one expression contains an expression that contains an expression that contains an expression that containsâ€¦

You are probably asking yourself how could we have an expression that contains an expression?

Well, as an example, Letâ€™s compose a nested expression that adds `3` and `4` and multiply the result by `5`.

For that, we are going to use again the 3 steps of an expression that we introduced in previous chapter:

1. First, you need to tell the computer that you want him to execute something. For that you use the parenthesis: `()`. The computer will execute for you the content of the parenthesis.

2. Then, you need to tell him what `operation` you want him to execute: in our case, the operation is the multiplication.

3. Finally, you need to tell him what are the details of the `operation`: the `operands`. In our case, the `operands` are: `(+ 3 4)` and `5`.

Combining all of that, we get:

``````(* (+ 3 4) 5)
``````

Congratulations! This is your first nested expression.

Now, try to use more `operands`: for instance, you could type `(* (+ 3 4) 5 6 8)`.

# Exercises

If you are having difficulties with one exercise, read again the details of the 3 steps of an expression.

A. add 10 to 12 and multiply the result by 3

``````()
``````

B. add 7 to 9 and multiply the result by 5

``````()
``````

C. multiply 7 and 9 and add 6 to the result

``````()
``````

D. multiply 7 and 9 and add 6 and 9 to the result

``````()
``````

E. add 7 to 9 and multiply the result by 5 and 3

``````()
``````

F. add 7 to 9 and multiply the result by `(+ 3 8 9)`

``````()
``````

Here are the solutions:

A. 66

B. 80

C. 69

D. 78

E. 240

F. 320

Send us a screenshot with your programs to viebel@gmail.com.

Now, you are ready for chapter 3.