Question 1125619
You are looking for this --------


{{{(x+123)+x=2438/2}}}

-

{{{2x+123=1219}}}

{{{2x=1096}}}

{{{x=548}}}



{{{system(DIMENSIONS,671,and,548)}}}










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Note that "around" and "along" are not the same thing.  If the description really meant "around the perimeter", then some further information and adjustment would be needed.