I need to write a simple formula but I cannot quite understand how to
do it in Excel.

I need to take the value of a cell (lets call it A8). I need to
subtract 15% from the value of A8. Then I need to take the resulting
value of that and subtract 2.9% from it. finally I need to subtract .3
from the final value. I need to to be displayed in cell B8. I know how
to enter formulas in Excel, but I can't get this one to run right (I
don't know how to reference the result of a earlier calculation in a
later calculation in the formula bar).

Thank you very much!