(1)6.2×9.9,
=6.2×(10-0.1),
=6.2×10-6.2×0.1,
=62-0.62,
=61.38;
(2)3.5×0.7+5.5×0.7+0.7,
=(3.5+5.5+1)×0.7,
=10×0.7,
=7;
(3)0.125×3.2×0.25,
=0.125×0.8×4×0.25,
=(0.125×0.8)×(4×0.25),
=0.1×1,
=0.1;
(4)0.8×(12.5-1.25),
=0.8×12.5-0.8×1.25,
=10-1,
=9;
(5)44.1÷3.5-7.5,
=12.6-7.5,
=5.1;
(6)18.36÷3.6×1.2,
=5.1×1.2,
=6.12;
(7)87.84÷1.6÷6.1,
=54.9÷6.1,
=9.