(1)8.5÷(5.2-3.5)+20.9,
=8.5÷1.7+20.9,
=5+20.9,
=25.9;
答:和是25.9.
(2)[1.28-(1.54-0.31)]×9.4,
=[1.28-1.23]×9.4,
=0.05×9.4,
=0.47.
答:积是0.47.
(1)8.5÷(5.2-3.5)+20.9,
=8.5÷1.7+20.9,
=5+20.9,
=25.9;
答:和是25.9.
(2)[1.28-(1.54-0.31)]×9.4,
=[1.28-1.23]×9.4,
=0.05×9.4,
=0.47.
答:积是0.47.