7z: Added output path example. (#1900)

pages/common/7z.md

@@ -10,6 +10,10 @@
 
 `7z x {{archived}}`
 
+- Extract an archive with user-defined output path:
+
+`7z x {{archived}} -o{{path/to/output}}`
+
 - Archive using a specific archive type:
 
 `7z a -t {{zip|gzip|bzip2|tar|...}} {{archived}} {{path/to/file}}`