Răspuns :
(x-1):10+90=670
(x-1):10=670-90
(x-1):10=580
(x-1)=580:10
(x-1)=58
x=58:1
x=58
(x-1):10=670-90
(x-1):10=580
(x-1)=580:10
(x-1)=58
x=58:1
x=58
(x-1):10+90= 134x5
(x-1):10+90=670
(x-1):10=670-90
(x-1):10=580
x-1=580x10
x-1=5800
x=5800+1
x=5801
(x-1):10+90=670
(x-1):10=670-90
(x-1):10=580
x-1=580x10
x-1=5800
x=5800+1
x=5801