2004x20022003
=(2000+4)×20022003
=2000×20022003+4×20022003
=40044006000+80088012
=40124094012
(115+217)x15x17
=332×15×17
=83×4×15×17
=83×60×17
=83×1020
=83×（1000+20）
=83000+1660
=84660