clarify how to show computation of inverse (MX2 checkit)

source/linear-algebra/exercises/outcomes/MX/MX2/template.xml

@@ -25,10 +25,10 @@ discussing its corresponding linear transformation.
                 </p>
                 <p>
 <!-- {{#invertible}} -->
-<m>{{label}}</m> is invertible.
+<m>{{label}}</m> is invertible because it is a bijective transformation.
 <!-- {{/invertible}} -->
 <!-- {{^invertible}} -->
-<m>{{label}}</m> is not invertible.
+<m>{{label}}</m> is not invertible because it is not a bijective transformation.
 <!-- {{/invertible}} -->
                 </p>
             </outtro>
@@ -62,9 +62,8 @@ be done without using technology.)
             <outtro>
                 <p>
 <!-- {{#invertible}} -->
-Show how to compute each column of the inverse matrix
-by solving an appropriate vector equation (that is, computing RREF
-of an appropriate augmented matrix).
+Show how to solve <m>{{label}} \vec x = \vec e_i</m> for <m>i=1,2,3,4</m> to obtain
+each column <m>{{label}}^{-1}\vec e_i</m> of the inverse matrix <m>{{label}}^{-1}</m>.
 <!-- {{/invertible}} -->
 <!-- {{^invertible}} -->
 N/A