45 + (71-х*9) = 80

(725*х-92) : 36=48*4

45 + (71-х*9) = 8045+71-9 х=80-9 х=-36

х=4

(725*х-92) : 36=48*4

(725*x-92) : 36 = 192

725x:36 = 1751:9

x = 1751:9 : (725:36)

x = 7004/725

х = 9.66068965517

45 + (71-х*9) = 80

71-х9=80-45

71-х9=35

71-35=х9

36=х9

х=36:9

х=4

Проверка

45 + (71-4*9) = 80

45+35=80

80=80

(725 х-92) : 36=48*4

(725 х-92) : 36=192

725 х-92=192*36

725 х-92=6912

725 х=6912+92

725 х=7004

х=7004:725

х=9,66