If you try to upload image to your post, and get this "Unable to create directory wp-content/uploads/... Is its parent directory writable by the server?" error message in WordPress, here is how I fix it.
Basically change wp-content file permission to 777, and once you can upload image, change it back to 755.
A video that might help: • Using FileZilla Secure FTP or SFTP Co...
If this somehow still doesn't work, talk to your host.