13/15.......4/9
общий знаменатель 45
39/45.......20/45
неравенство верно
1,2 + 3/10x = 8/15x + 0.78
3/10x - 8/15x = 0.78 - 1.2
9/30x - 16/30x = -0.42
-7/30x = -0.42 | * (-1)
7/30x = 0.42
x = 0.42 : 7/30
x = 0.42 * 30/7
x = 0.6 * 30
x = 1.8
2 1/3:х=3 3/4:1 1/8
2 1/3:х=15/4*8/3
2 1/3:х=10/3
х=7/3*3/10
х=7/10