3889 + 12.808 - ?  3854.002 ------------------------------------------------------------------------------------------------------------------------------
Нека 3889 + 12.808 - х  3854.002 . след това х  ( 3889 + 12.808 ) - 3854.002  3901.808 - 3854.002  47.806 . отговор  c
subtract(add(3889, 12.808), 3854.002)