38 + х = 72 + (72 : 6) - х
38 + х = 72 + 12 - х
х + х = 72 + 12 - 38
2х = 84 - 38
2х = 46
х = 23
-----------------------------------
(51 + 33) : х = 84 : 4
84 : х = 21
21 * х = 84
21х = 84
х = 4
-----------------------------------
1/4х = 1/3 * 1/4
1/4х = 1/12
х = 1/12 : 1/4
х = 1/3