Пошаговое объяснение:
( * -) + -а = - - а
- - *
- - = = - = -
(5/6+а)-3/4 = 5/6 - 3/4 + а = 10/12 - 9/12 + а = 1/12 + а
при а = 7/12.
1/12 + 7/12 = 8/12 = 2/3
Пошаговое объяснение:
(
* -
) + -
а = -
-
а
-
-
* 
-
-
=
= -
= - 
(5/6+а)-3/4 = 5/6 - 3/4 + а = 10/12 - 9/12 + а = 1/12 + а
при а = 7/12.
1/12 + 7/12 = 8/12 = 2/3