Need to calculate a percentage in fillable pdf and can't get the code right

I'm creating a worksheet meant to help with budgeting, adding up expenses and calculated a percentage based off of a number that is the total of two salary inputs. 

One of the fields is meant to calculate %50 percent of the total salary. 

Here's the code I'm using:

var Salary_Total = getField("Salary_Total").value;

var percentToGet = 0.50;

var percent = (percentToGet / 100) * number;

event.value = Salary_Total * Percentage;

What am I doing wrong here?