х+460=660, х-380=240, х÷40=640

x+460=660
x=660-460
x=200
200+460=660
660=660

x-380=240
x=380+240
x=620
620-380=240
240=240

x:40=640
x=640*40
x=25.600
25.600:40=640
640=640