7х-4(х-2(х-5(х-6)))=21

7х-4(х-2(х-5(х-6)))=21,7х - 4х  + 8 (х - 5 (х - 6)) = 21,
7х - 4х + 8х - 40 (х - 6 ) = 21,
7х - 4х + 8х - 40х + 240 = 21,
- 29 х = - 240 + 21,
-29х = -219.
х= 219/29
х=7 целых 16/29