Oh yeah system partition is read only, the easiest way is If you have root explorer or es file manager use it to change permissions of trinity at system/bin/trinity to rwxr-xr-x otherwise if you want to do it from terminal run these commands after "su"It says:
"Unable to chmod /system/bin/trinity: Read-only file system"
"mount -o rw,remount /system"
"chmod 744 system/bin/trinity"
"trinity"