(1)9.4×[1.28-(1.54-0.31)],
=9.4×[1.28-1.23],
=9.4×0.05,
=0.47;
(2)20-[7.8+(6.2+1.29)],
=20-[(7.8+6.2)+1.29],
=20-[14+1.29],
=20-15.29,
=4.71;
(3)0.25×2.73×4,
=0.25×4×2.73,
=1×2.73,
=2.73;
(4)799×99,
=799×(100-1),
=799×100-799×1,
=79900-799,
=79101.
(1)9.4×[1.28-(1.54-0.31)],
=9.4×[1.28-1.23],
=9.4×0.05,
=0.47;
(2)20-[7.8+(6.2+1.29)],
=20-[(7.8+6.2)+1.29],
=20-[14+1.29],
=20-15.29,
=4.71;
(3)0.25×2.73×4,
=0.25×4×2.73,
=1×2.73,
=2.73;
(4)799×99,
=799×(100-1),
=799×100-799×1,
=79900-799,
=79101.