# variables
Variables are used to store data. Each variable has a name and holds a value. Think of it like a box: slap on a label, and it can store stuff. š¦
The variable name can consist of letters, numbers, and the _ underscore.
These are all valid variable names and values:
```python
name = 'Joe'
name2 = 'Joseph'
user_id = 26789437849
progress = 0.75
xp = 60
verified = True
```
We can also change the value of a variable or print it out:
```python
xp = 70
xp = 80
print(xp) # Output: 80
```
Here, we are assigning the number value 70 to the variable xp. Then, we are reassigning the number value 80 to the same variable. And printing it out.
# data types
## integer
An integer, or int, is a whole number. It has no decimal point and contains the number 0, positive and negative counting numbers.
```python
year = 2025
age = 32
```
## float
A floating-point number, or a float, is a decimal number. It can be used to represent fractions or precise measurements.
```python
pi = 3.14159
meal_cost = 12.99
```
## string
A string, or str, is used for storing text. Strings are wrapped in double quotes " " or single quotes ' '.
```python
message = "good nite"
username = '@snoopdogg'
```
## boolean
A Boolean data type, or bool, stores a value that can only be either true or false.
```python
late_to_class = False
cranky = True
```
# operators
`x + y` | Sum of two numbers
`x - y` | Difference of two numbers
`x * y` | Product of two numbers
`x / y` | Quotient of two numbers
`x // y` | Quotient of two numbers, returned as an integer
`x % y` | x "modulo" y: The remainder of x / y for positive x, y
`x ** y` | x raised to the power y
`-x` | A negated number
`abs(x)` | The absolute value of a number
`x == y` | Check if two numbers have the same value
`x != y` | Check if two numbers have different values
`x > y` | Check if x is greater than y
`x >= y` | Check if x is greater than or equal to y
`x < y` | Check if x is less than y
`x <= y` | Check if x is less than or equal to y
## using operators
Operators can be used to alter numbers (and sometimes strings).
```python
print(2 + 3) # Output: 5
```
```python
print("Hello " + "World") # Output: Hello World
```
## operators with variables
Operators can also be used with variables. That can help you keep track of what you're doing.
```python
pizza = 2.99
coke = 0.99
total = pizza + coke
tip = total * 0.2
print(tip) # Output: 0.796
```
# instructions
Complete each of the following challenges using variables, operators, and `print()`.
**Challenge 1**
> Create a program that determines the sales tax for a given price. It should `print()` the sales tax and the total including the tax.
**Challenge 2**
> Create a program that determines the tip you should give at a restaurant. It should start with the total (dollar amount), calculate taxes and a 20% tip, and `print()` the original total, tax, tip, and grand total.
**Challenge 3**
> Create a program that converts a number from Fahrenheit (F) to Celsius (C).
>
> $
> C = \frac{5}{9} \cdot (F - 32)
> $
>
> `print()` the result.