①0.75×4×0.25×4,
=0.75×(4×0.25)×4,
=0.75×1×4,
=3;
②9.6+9.9×99,
=9.6+980.1,
=989.7;
③15.58÷8.2-0.72,
=1.9-0.72,
=1.18;
④4.536÷0.8÷14,
=5.67÷14,
=0.405;
⑤2.8×3.6+1.4×2.8,
=(3.6+1.4)×2.8,
=5×2.8,
=14;
⑥6.3×10.1,
=6.3×(10+0.1),
=6.3×10+6.3×0.1,
=63+0.63,
=63.63.