linear algebra – Percentage from Total

I have a table to calculate percentage of numbers. Below are the numbers in the table. In this table how can I find total (in below table the column E) (2.142785) from totals from column A,B, C??

Click here to see the table

Means how can I find 2.142785 from 8198, 491 and 66? What formula I can use to find the percentage of values from total values? Any help would be really appreciate. Thanks