Номер 1097
1) –15 + 9 + (–9) + 15 = –15 + 15 + 9 + (–9) = 0;
2) –35 + (–19) + 28 + 19 = –35 + 28 + (–19) + 19 = –7;
3) 2,47 + (–2,11) + (–7,89) + 6,53 = (2,47 + 6,53) + ((–2,11) + (–7,89)) = 9 + (–10) = –1;
4) 1,9 + (–3) + (–1,9) + 9 + (–2) = 1,9 + (–1,9) + (–3) + (–2) + 9 = –5 + 9 = –4.