你的裤子穿反了。

You've got your trousers on ___back ___to ___front.

她不小心穿反了毛衣去参加派对。

She accidentally wore her sweater ___back ___to ___front to the party.

电池被装反了，所以设备无法工作。

The battery was inserted ___back ___to ___front, so the device didn't work.