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The “compute” part of “computer” means we cannot leave what computers do best out of this lesson! We can compute new values for our variables with arithmetic operators.

This is useful when we work with values that need to be numerically changed. Let’s take a look at this in action:

``````player1Score = 0
player1Score = player1Score + 1
print(player1Score)
--output: 1``````

The syntax may look a bit strange at first. Let’s break it down. Recall that `=` means you’re assigning what is on the right of `=` to the variable on its left. To understand this, we need to evaluate the expression on the right first (`player1Score + 1`), then reassign it back to the left variable (`player1Score`).

• On the right is `player1Score + 1`
• We first access the value of `player1Score` that is currently at `0`
• Replace `player1Score` with its current value and we get `0 + 1` which equals `1`
• Then, the `=` assigns the new value back into `player1Score`
• Now, `player1Score` will have a new value of `1`

If we were to add the same line of code again with the newly updated value, what do you think it will be?

``````player1Score = player1Score + 1
print(player1Score)``````

Since `player1Score` starts out with `1` from the previous calculation, adding `1` to the variable means `1 + 1`. `player1Score` will now have the number `2`!

Other arithmetic operators work with variables too — see the example below and also Lua’s documentation:

Operator Example
Addition myVariable = myVariable + 1
Subtraction myVariable = myVariable - 1
Multiplication myVariable = myVariable * 1
Division myVariable = myVariable / 1
Exponentiation myVariable = myVariable ^ 1
Remainder myVariable = myVariable % 1
Negation myVariable = -myVariable

### Instructions

1.

In our game, Kamala scores one point!

Add `1` to the `player1Score` variable and use `print()` to output the modified `player1Score`.

2.

Foul! Bruno loses 2 points.

Subtract `2` from the player2Score variable and use `print()` to output the modified `player2Score`

3.

C-C-Combo! Bruno gets a point multiplier, multiply the `player2Score` variable by `1.5` and use `print()` to output the modified `player2Score`.