(1)70.8-1.25-1.75,
=70.8-(1.25+1.75),
=70.8-3,
=67.8;
(2)5.81+8.3+4.19+11.7,
=(5.81+4.19)+(8.3+11.7),
=10+20,
=30;
(3)8.7×9.9,
=8.7×(10-0.1),
=8.7×10-8.7×0.1,
=87-0.87,
=86.13;
(4)0.25×17.3×0.4,
=0.25×0.4×17.3,
=0.1×17.3,
=1.73;
(5)0.15×9+0.15,
=0.15×(9+1),
=0.15×10,
=1.5;
(6)3.54×0.29-0.29×2.54,
=(3.54-2.54)×0.29,
=1×0.29,
=0.29.