# Arithmetic in Lua

Lua can do arithmetic. While you're using Lua you're going to be using it a lot, so I'll teach you how to use it.

Lets make a variable called myNumber, and set it to 0. Start out by writing this:

```function whatIsMyNumber()
print("myNumber is "..myNumber)
end

print("Setting myNumber to 0")
myNumber=0```

Notice that we do not use quotes here! myNumber is a number, not text! We can't do math on text, so we leave the quotes off to show it's a number.

Now write the following below it so we can check it:

`whatIsMyNumber()`

This calls whatIsMyNumber, the function we made above, and it will tell us what myNumber is. We'll be calling it several times which is why I made a function.

So far you should have:

```function whatIsMyNumber()
print("myNumber is "..myNumber)
end

print("Setting myNumber to 0")
myNumber=0
whatIsMyNumber() ```

Now, move two lines down with enter and type the following:

```print("Setting myNumber to 5 + 5")
myNumber=5 + 5
whatIsMyNumber() ```

This is your first arithmetic in Lua. To add two numbers, you just need to do number+ number. It's that simple.

Likewise for subtraction. To subtract two numbers you just need to do number - number.

Go down two lines and write this:

```print("Setting myNumber to 10 - 5")
myNumber=10 - 5
whatIsMyNumber() ```

Multiplication and division use special symbols. Multiplication uses an asterisk (an *), the little five sided star thing. To multiply you just need to do number * number.

Like we did for the last two, go down two lines and write this:

```print("Setting myNumber to 5 times 5")
myNumber=5 * 5
whatIsMyNumber()```

Lastly, division uses a forward slash. To divide you just need to do number / number.

Like we did for the last two, go down two lines and write this:

```print("Setting myNumber to 25 divided by 5")
myNumber=25 / 5
whatIsMyNumber() ```

Now say you want to add a number to a variable, to a number you initially don't know.

```print("Adding 5 to myNumber.")
myNumber=myNumber+5
whatIsMyNumber() ```

So try it out. Save the file as arith.lua and open it in Garry's Mod.