X÷30=1000-850
х=(1000-850)*30
х=150*30
х=4500
850-c=230+480+69
-с=230+480+69-850
-с=-71
с=71
78+a=684÷2
78+a = 342
a = 342-78
a = 264
30×x=900-660
30x = 300
x = 300÷30
x = 10
X÷30=1000-850
х=(1000-850)*30
х=150*30
х=4500
850-c=230+480+69
-с=230+480+69-850
-с=-71
с=71
78+a=684÷2
78+a = 342
a = 342-78
a = 264
30×x=900-660
30x = 300
x = 300÷30
x = 10