b/ 6=13
b=78
900 / b=9
b=8100
70x=560
x=8
57+b/ 6=70
в/6=70-57
в/6 = 13
в= 13*6
в=78
900 / b -3 =6
900/в = 6+3
900/в= 9
в= 900:9
в=100
70 * x - 20= 540
70*х=540+20
70*х=560
х=560 : 70
х=8
b/ 6=13
b=78
900 / b=9
b=8100
70x=560
x=8
57+b/ 6=70
в/6=70-57
в/6 = 13
в= 13*6
в=78
900 / b -3 =6
900/в = 6+3
900/в= 9
в= 900:9
в=100
70 * x - 20= 540
70*х=540+20
70*х=560
х=560 : 70
х=8