40.9/5又2/19-4.09x9/97+1.1x4又21/97
=40.9÷97/19-4.09×9/97+1.1×409/97
=40.9×19/97-4.09×9/97+11×40.9/97
=40.9/97×(19-0.9+11)
=40.9/97×29.1
=781.19/97