When evaluating an expression, the normal mathematical rules are used.

a = 2 * b + 3

In this case the expression “2 * b” is first evaluated and then 3 is added to the result.

Parentheses ( ) can be used to ensured that an expression is evaluated in a certain way.

a = 2 * (b + 3)

In this case the expression “b + 3” is first evaluated and then multiplied by 2.

a = (12+a) / (30+b)

In this example the expression (12 + a) is evaluated first. Then the expression (30 + b) is evaluated and finally the result of the first expression is divided by the result of the second expression.