so you need both of the packages installed: the common one should be installed first; and then the specific (MG2100series) package;
the hidden how-to of running scangear is to type
scangearmp
into a terminal
...........and hit ENTER.........that should open up scangear in all its glory: scangearmp is written by Canon;
.......if this all works, you would be best with a launcher; I use Mint 13 Mate so I go to bottom bar; right-click and select ADD to PANEL
.........see thumbnail below ......... call it whatever you want...........command MUST BE as above ie scangearmp
.....you can change the default icon if you wish.........