Question 829773
Let WHAT equal the length of the rectangle?  

Use this little change.  Let L equal the length of the rectangle.


If width is 10 mm shorter than L, then this means L is 10 mm more than the width.  Either way, you have these:


Length is L
Width is L-10
Also given is perimeter.  2(L+w)=244, using w for width.
Putting in all the expressions, 2(L+(L-10))=244, and you want to find the value for L.


2(L+(L-10))=244
2(2L-10)=244
2L-10=122
L-5=61
L=66---------part of the result, the main important result for the solution