(4 x 1000) + ( 8 + 100) + (1 + 10) + (0 x 1) + (8 x .1) + (2 x .01)

Let me google that for you (http://lmgtfy.com/?q=bodmas)

This is not an order of operations question, but rather it's about the powers of ten that are represented by the place of digits in a number. For example the number 567.3 = 5x100 + 6x10 +7x1 + 3x0.1.

To the OP: performing the operation is straight-forward - do you have a specific question? Buy the way, it appears you have a typo for the quantity in the tens place.