Номер 1133

1) –2 + (–3) + (–8) + (–7) = (–2 + (–8)) + (–3 + (–7)) = –10 + (–10) = –20;

2) 13 + 26 + (–3) + (–16) = (13 + (–3)) + (26 + (–16)) = 10 + 10 = 20;

3) –119 + 19,7 + (–91) = (–119 + (–91)) + 19,7 = –200 + 19,7 = –180,3;

4) 78,2 + (–105) + 11,8 = (78,2 + 11,8) + (–105) = 90 + (–105) = –15.