1053,
1) 7 - 3/5 + 2 7/9 =(НОК(5,9)=45) = 9 + (-27+35)/45 = 9 8/45 - ОТВЕТ
2) 5 2/7 - 1/3 + 6 = 5+6 + (2/7 - 1/3) = НОК(3,7)=21) = 11 + (6-7)/21 = 10 20/21 - ОТВЕТ
3) 9 + 1 3/4 - 2/5 = 9+1 + (3/4 - 2/5)= НОК(4,5)=20) = 10 +(15-8)/20 = 10 7/20 - ОТВЕТ
4) НОК(5,12,60)=60
3 5/12 - 4/5 + 31/60 = 3 + (25-48+31)/60 = 3 8/60 = 3 2/15 - ОТВЕТ