1) 90720:(207:23⋅840);207:23=9; 9⋅840=7560; 90720:7560=12;
2) 19392:48⋅(510:5);510:5=102; 19392:48=404; 404⋅102=41208;
3) 14700:21:7⋅49; 700:7=100; 100⋅49=4900;
4) 280:20:(56:8):(14:7);280:20=14; 56:8=7; 14:7=2; 14:7:2=2:2=1.
Ответ: 1) 12; 2) 41 208; 3) 4900; 4) 1.