18 • (b - 7х) = 90
18 b - 126х = 90
-126х = 90 - 18b
-126х = 90 - 18 • 40
-126х = 90 - 720
-126х = -630
х = -630 : (-126)
х = 5
18 • (b - 7х) = 90
18 b - 126х = 90
-126х = 90 - 18b
-126х = 90 - 18 • 40
-126х = 90 - 720
-126х = -630
х = -630 : (-126)
х = 5