7х-4(х-2(х-5(х-6)))=21
раскроем скобки
7x-4x+8x-40x+240 = 21
-29x+219 = 0
29x-219 = 0
29x = 219
x = 219/29
х=7,55172413793
7х-4(х-2(х-5(х-6)))=21
раскроем скобки
7x-4x+8x-40x+240 = 21
-29x+219 = 0
29x-219 = 0
29x = 219
x = 219/29
х=7,55172413793