ответ. Здесь. Внизу.
а)
11/30+7/12 = 22/60+35/60 = 57/60 = 19/20,
б)
1/27+5/18 = 2/54+15/54 = 17/54,
в)
5/21-5/28 = 20/84-15/84 = 5/84,
г)
11/18-7/12 = 22/36-21/36 = 1/36
ответ. Здесь. Внизу.
а)
11/30+7/12 = 22/60+35/60 = 57/60 = 19/20,
б)
1/27+5/18 = 2/54+15/54 = 17/54,
в)
5/21-5/28 = 20/84-15/84 = 5/84,
г)
11/18-7/12 = 22/36-21/36 = 1/36