Схема а) :
х + 16 = 25
х = 25 - 16
х = 9
-----------------
9 + 16 = 25
25 = 25
25 - х = 16
х = 25 - 16
х = 9
------------------
25 - 9 = 16
16 = 16
16 + х = 25
х = 25 - 16
х = 9
------------------
16 + 9 = 25
25 = 25
схема б) :
650 - х = 540
х = 650 - 540
х = 110
------------------------
650 - 110 = 540
540 = 540
540 + х = 650
х = 650 - 540
х = 110
------------------------
540 + 110 = 650
650 = 650
х + 540 = 650
х = 650 - 540
х = 110
------------------------
110 + 540 = 650
650 = 650