Question 383980
Suppose the width is w and the length is 4+w. We have

{{{w(4 + w) = 77}}}

{{{w^2 + 4w - 77 = 0}}}

This factors to

{{{(w + 11)(w - 7) = 0}}}

Therefore the only (positive) root is w = 7. Therefore the length is 11.