Б) 2/18 + с = 1 - 12/18
2/18 + с = 18/18 - 12/18
2/18 + с = 6/18
с = 6/18 - 2/18
с = 4/18= 2/9
в)1 - а = 130/300 + 90/300
1 - а = 220/300
-а = 220/300 - 1
-а = 220/300 - 300/300
а= 300/300 - 220/300
а= 80/300 = 8/30 = 4/15
г) к : 100 = 3/3
к : 100 = 1
к = 100 * 1
к = 100