Comment 3 for bug 769241

Libmotif4 is supposed to be installed
bill@bill-GA-MA78GM-US2H:~$ apt-cache policy libmotif4libmotif4:
  Installed: (none)
  Candidate: 2.3.3-5ubuntu1
  Version table:
     2.3.3-5ubuntu1 0
        500 http://archive.ubuntu.com/ubuntu/ natty/multiverse amd64 Packagesbill@bill-GA-MA78GM-US2H:~$

This package is the driver for the Brother DCP-7040
 sudo dpkg -i --force-depends /home/bill/Downloads/brdcp7040lpr-2.0.2-1.i386.deb
[sudo] password for bill:
dpkg: error processing /home/bill/Downloads/brdcp7040lpr-2.0.2-1.i386.deb (--install):
 package architecture (i386) does not match system (amd64)
Errors were encountered while processing:
 /home/bill/Downloads/brdcp7040lpr-2.0.2-1.i386.deb
As you can see i386 and amd64 will not coexist.

bill@bill-GA-MA78GM-US2H:~$ sudo apt-get install libmotif4:i386-2.3.3-5Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package libmotif4:i386-2.3.3-5
E: Couldn't find any package by regex 'libmotif4:i386-2.3.3-5'

Now attempting to install the amd64 version
bill@bill-GA-MA78GM-US2H:~$ sudo apt-get install libmotif4
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
  libmotif4
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,417 kB of archives.
After this operation, 3,793 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu/ natty/multiverse libmotif4 amd64 2.3.3-5ubuntu1 [1,417 kB]
Fetched 1,417 kB in 32s (43.6 kB/s)
Selecting previously deselected package libmotif4.
(Reading database ... 384708 files and directories currently installed.)
Unpacking libmotif4 (from .../libmotif4_2.3.3-5ubuntu1_amd64.deb) ...
Setting up libmotif4 (2.3.3-5ubuntu1) ...
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place

Note that I still cannot install the driver
bill@bill-GA-MA78GM-US2H:~$ sudo dpkg -i --force-depends /home/bill/Downloads/brdcp7040lpr-2.0.2-1.i386.deb
dpkg: error processing /home/bill/Downloads/brdcp7040lpr-2.0.2-1.i386.deb (--install):
 package architecture (i386) does not match system (amd64)
Errors were encountered while processing:
 /home/bill/Downloads/brdcp7040lpr-2.0.2-1.i386.deb

This is a dead end and I cannot go further to solve my problem.
Why can't i386 and amd64 exist side by side?
All users trying to install drivers are finding this problem