- (3х - 5) - 2 + (7 - х) = 15
- 3х + 5 - 2 + 7 - х = 15
- 3х + 10 - х = 15
- 3х - х = 15 - 10
- 4х = 5
х = 5 : (- 4)
х = - 5/4
-------------------------------------
- (3 * (- 5/4) - 5) - 2 + (7 - (- 5/4)) = 15
- (- 15/4 - 5) - 2 + (7 + 5/4) = 15
- (- 15/4 - 20/4) - 2 + (28/4 + 5/4) = 15
- (- 35/4) - 2 + 33/4 = 15
35/4 - 2 + 33/4 = 15
35/4 - 8/4 + 33/4 = 15
60/4 = 15
15 = 15