①4×0.8×2.5×12.5,
=(4×2.5)×(0.8×12.5),
=10×10,
=100;
②
2
15 ÷[1-(
1
5 +
1
3 )],
=
2
15 ÷ [1-
8
15 ],
=
2
15 ÷
7
15 ,
=
2
15 ×
15
7 ,
=
2
7 ;
③(2.8+3.85÷3.5)×4.6,
=(2.8+1.1)×4.6,
=3.9×4.6,
=(4-0.1)×4.6,
=4×4.6-0.1×4.6,
=18.4-0.46,
=17.94;
④6.5×1.83+0.17×6.5,
=(1.83+0.17)×6.5,
=2×6.5,
=13.