$a + $b = 13
Adds the value of $b to $a.
$a - $b = 7
Subtracts the value of $b from $a.
$a * $b = 30
Multiplies the value of $b by $a.
$a / $b = 3.3333333333333
Divides the value of $a by $b.
$a % $b = 1
Gives the remainder left over after dividing $a by $b.