x=590+280
x=870
(900-100):x=80
800:x=80
800:80=x
x=10
1. x-280=590
870-280=590
2.(900-100):×=80
×=900-100
=800
×=800:80
×=100
(900-100):100=80
x=590+280
x=870
(900-100):x=80
800:x=80
800:80=x
x=10
1. x-280=590
x=590+280
x=870
870-280=590
2.(900-100):×=80
×=900-100
=800
800:x=80
×=800:80
×=100
(900-100):100=80