3/4 : х = 1 1/5 : 1 1/3
3/4 : х = 6/5 : 4/3
3/4 : х = 6/5 * 3/4
3/4 : х = 3/5 * 3/2
3/4 : х = 9/10
х = 3/4 : 9/10
х = 3/4 * 10/9
х = 1/2 * 5/3
х = 5/6
2/х - 0,4 = 1/0,4
2/х - 4/10 = 1 : 4/10
2 / х - 4/10 = 1/1 * 10/4
2 / х - 4/10 = 10/4
х - 4/10 = 2 : 10/4
х - 4/10 = 2/1 * 4/10
х - 4/10 = 8/10 = 4/5
х = 4/5 + 4/10
х = 4/5 + 2/5
х = 6/5
х = 1 1/5